Table of Contents

Lumbosacral Plexus Lesions

Overview of Lumbosacral Plexopathy

Upper lumbar plexus lesions demonstrate various combinations of deficits in the iliohypogastric, ilioinguinal, genitofemoral, femoral and obturator nerve distributions. Weakness is seen in hip flexion, knee extension (concomitant inability to lock the leg on standing) and adduction of the thigh. Sensory loss is noted in the lower abdominal wall, inguinal, labial, and scrotal areas as well as the thigh and medial lower leg. An absent or a depressed knee reflex is noted.

Lower lumbar sacral plexus lesions cause deficits within the innervation territories of the gluteal, sciatic, tibial, and peroneal nerves. Weakness occurs in hip extension, and abduction, knee flexion, and all intrinsic foot musculature. Sensory loss occurs in the posterior thigh, anterior and posterior aspects of the lower leg below the knee and most of the foot. There are diminished or absent ankle reflexes. Gluteal and sciatic nerve weakness localizes a lesion to the sacral plexus.

Plexopathies are recognized when motor, sensory, and reflex deficits occur in multiple nerve and segmental distributions that affect one extremity.

Localization is often difficult due to the pathologies of the region, but usually in a broad sense can be divided into:

1.Lumbar plexopathy

2.Sacral plexopathy

3.Lumbosacral trunk lesions

4.Pan-plexopathy

In general, lumbar plexopathies evolve in a stepwise and dissociated manner.

In localization of lumbosacral plexopathies pathology of the cauda equina and conus medullaris has to be considered. Rarely, motor neuron disease may simulate plexopathy if deficits are without pain or sensory loss. Intraspinal lesions (lower spinal cord) tend to be bilateral with early bowel and bladder dysfunction rather than motor weakness. Cauda equina lesions are painful, and bladder dysfunction is seen early.

Differential points in the history or examination include:

  1. Pain in the following territories define specific sensory roots and nerves:
    1. Hip (sclerotomal radiation of L5)
    2. Buttock (L5-S1 root); often have tenderness in the sciatic notch
    3. Proximal thigh laterally (L5); also may be caused by bursitis of the tensor fascia lata
    4. L1, L2, L3 roots innervate the dorsal thigh; this is also the sclerotomal distribution of the recurrent nerve of Spurling of L5. The usual problem is disc herniation that causes radiation to the dorsal thigh rather than its somatic dermatomal distribution.
    5. The medial thigh is innervated by the ilioinguinal nerve (L1, L2 roots)
    6. The groin is innervated by T12 and L1. It may also have a projected sclerotomal radiation from S1. Thus, S1 root irritation may radiate to the groin. This invariably is diagnosed as hip disease or an inguinal hernia.
    7. The straight leg raising test causes sciatic nerve pain (L5-S1 roots); the reverse SLR test stretches the femoral nerve (L2-L3 sensory roots are involved; often concomitant inguinal pain).
    8. In plexopathy, the Valsalva maneuver does not elicit pain as it frequently does with radiculopathy
    9. In peroneal nerve neuropathy with foot drop:

i.Inversion of the foot is normal

ii.Toe flexion and hip abduction are normal

iii.The ankle reflex is preserved

    1. Differential signs to distinguish lumbosacral trunk lesions from an L5 radiculopathy:

i.The lumbar trunk is formed primarily by the L5 spinal nerve with a contribution from L4; peroneal sensation is normal which favors a trunk lesion.

ii.If the pattern of weakness is hip adductors, iliopsoas, and quadriceps a lumbar plexopathy rather than femoral or obturator nerve lesions is more likely

    1. Simultaneous involvement of the lumbar and sacral roots is usual with external trauma; iatrogenic injury more often involves individual L5 plexus components.

Anatomical Relationship of the Lumbar and Sacral Plexus

1.The L1, L2, L3 ventral rami are the primary components of the lumbar plexus with contributions from T11 and T12.

a.They traverse the posterior portion of the psoas muscle anterior to the vertebral transverse processes:

i.Femoral nerve (L2-L4 primary spinal nerves) also supplies sensation to the thigh and leg by:

1.Medial and intermediate nerve of the thigh

2.Saphenous nerve which provides sensation to the medial calf

2. Obturator nerve (L2-L4 spinal nerves):

a. Innervates the adductor muscles of the thigh

b. Provide cutaneous innervations to the medial thigh

3. Muscular branches that derive directly from the plexus:

a. Iliopsoas (L1-L3 spinal nerves)

b. Iliacus (L2-L3 spinal nerves)

4. Sensory nerves of the lumbar plexus:

a. Iliohypogastric (L1 spinal root)

b. Ilioinguinal nerve (L1 root) innervates:

i. Upper medial thigh

ii. Base of the penis and labia majora

c. Genitofemoral nerve (L1-L2 root):

i.Innervates the upper anterior thigh

ii.Scrotum and labia majora

d. Lateral cutaneous nerve of the thigh (L2-L3)

5. Lesions of the entire lumbosacral plexus:

a.Are rare; most are incomplete

b.Paralysis or paresis of the entire lower extremity with hypo or areflexia

c.Sensory abnormalities that involve the entire lower extremity

6. Lesions of lumbar segments:

a.Usually are incomplete

b.Paresis and atrophy in the distribution of the femoral and obturator nerves:

i. Iliopsoas:

1) Weakness of thigh flexion

ii. Quadriceps:

1) Weakness of leg extension

iii. Sartorius:

1) Weakness of thigh eversion

iv. Adductor muscles:

1) Weakness of thigh adduction

    1. Sensory signs:

i.Sensory loss in the inguinal area and over the genitalia

1.Iliohypogastric, ilioinguinal, and genitofemoral nerves are involved

ii.Lateral thigh:

1.Lateral femoral cutaneous nerve

iii.Medial thigh:

1.Obturator nerve

iv.Anterior thigh:

1.Femoral nerve

v.Medial part of the lower leg:

1.Saphenous nerve that is derived from the femoral nerve

Reflexes

  1. Depressed or absent patellar reflex:

a.Femoral nerve

  1. Loss of cremasteric reflex:

a.Genitofemoral nerve

Sacral Plexus

General Characteristics

  1. S1-S3 ventral rami are the major roots:
    1. Contribution from L4-L5 and S4-S5 roots
  2. The plexus overlies the lateral sacrum and the posterior lateral pelvic wall
  3. Sciatic nerve (spinal nerves L4, L5, S1-S3):
    1. Innervates the hamstrings; all muscles below the knee
    2. All sensation below the knee except that supplied by the saphenous nerve (medial lower leg):
    3. At the sciatic notch it divides into the common peroneal and tibial nerves
  4. Superior gluteal nerve (L4, L5 S1 spinal nerves):
    1. Innervates the gluteus medius and minimus muscles
  5. Inferior gluteal nerve (L5, S1, S2 spinal nerves):
    1. Innervates the gluteus maximus muscles
  6. Posterior femoral cutaneous nerve (S1, S2, S3):
    1. Innervates the buttocks, perineum, posterior thigh

i.The cuneal branch innervates the posterior upper thigh and inferior buttock

Lesions of the Sacral Plexus

Complete Lesion

  1. Motor signs:
    1. Paralysis or paresis of muscles innervated by the superior gluteal, inferior gluteal and the sciatic nerves

i.“Flail foot” from paralysis of both the dorsal and plantar foot musculature

    1. Weakness:

i.Knee flexion:

1.Hamstrings

ii.Foot eversion:

1.Peroneal

    1. Foot inversion (L4-S1 spinal roots):

i.Tibialis anterior and posterior tibial nerve

    1. Plantar flexion of the toes:

i.Medial plantar nerves (II – V digits)

ii.Tibial nerve innervates the flexor hallucis longus

    1. Extension of the toes:

i. Peroneal nerve innervates the extensor hallucis longus; L5-S1 roots

ii. Deep fibular nerve (Extensor hallucis longus muscle – EHL)

f. Abduction and internal rotation of the thigh:

i. Superior gluteal nerve

g. Hip extension:

i.Inferior gluteal nerve

Sensory Signs

1.Loss of sensation in the sciatic nerve distribution:

a.Outer leg

b.Dorsum, sole and inner aspect of the foot

2.Posterior thigh and popliteal fossa:

a.Posterior femoral cutaneous nerve

Reflexes

1.Decreased Achilles reflex:

a.Sciatic nerve

2.Depressed bulbocavernosus reflex

Sphincter Signs

1.Loss or dysfunction of bladder and bowel control:

a.Pudendal nerve

Differential Diagnosis Features between Root and Lumbosacral Plexus Lesions

1.Positive mechanical signs favor a root lesion:

a.Straight leg raising test (sciatic nerve and S1 root)

b.Reverse SLR (places traction on the femoral nerve); the leg is extended with the patient lying on his stomach

c.Valsalva maneuver that causes pain:

i.Root greater than plexus involvement

2.Warm, dry and red foot:

a.Indicative of a plexus lesion

b.Involvement of the retroperitoneal lumbar sympathetic nerves

3.Proximal > distal leg muscle weakness suggests a plexus lesion

4.Gluteus muscle innervations arise directly from the plexus

5.Iliopsoas muscle is not involved in a femoral nerve lesion because its innervation is directly from the plexus

Trauma of the Lumbosacral Plexus

General Characteristics

  1. The lumbosacral plexus is often injured with trauma to the pelvic ring:

a.Double fracture dislocation

b.Traction injury from dislocation of the hip joint

  1. Femoral nerve compression due to position:
    1. Occupies the gutter between the psoas and iliopsoas muscle above the inguinal ligament:

i.Surgical retraction (medially)

ii.Injured laterally by a hematoma between the iliacus fascia and the nerve

  1. The lumbosacral cords are vulnerable to compression at the:

a.Pelvis brim by the fetal head

b.Obstetric forceps

  1. Aneurysm of the common iliac or hypogastric arteries in the presacral areas
  2. The femoral nerve is compressed by:

a.Angulation under the inguinal ligament

b.Prolonged flexion abduction of the thigh (dorsal lithotomy position under anesthesia)

  1. Fixation points of the common peroneal nerve are at the sciatic notch and fibular neck:
    1. Vulnerable to traction injury

Clinical Manifestations

  1. Fracture:
    1. Double vertical fracture dislocations of the pelvic bony ring:

i.50% of patients suffer neurologic deficits

    1. The injury is usually ipsilateral to the iliac joint damage
    2. The lumbosacral plexus cord level is affected by consequent compromise of L5-S1 spinal nerve innervated muscles
  1. Rupture, compression and traction injuries affect:
    1. Lumbosacral trunk:

i.Primarily L4 and L5 spinal nerves (L5 primarily)

ii.The spinal nerves are contiguous with the sacrum adjacent to the sacroiliac joint.

b.Obturator and or superior gluteal nerves are often concomitantly injured

c.L5-S3 anterior rami may be affected

d.Concomitant vertebral body rupture

  1. Intra-arterial injections:

a.Injections into the buttock:

i.Ischemic injury due to vasoactive drugs that are injected into the inferior gluteal artery causing ischemia of the sciatic nerve

ii.Weakness, pain, and sensory loss in the sciatic nerve distribution occur minutes to a few hours after the injection

iii.Widespread lumbar plexus injury may occur due to retrograde extension of gluteal artery spasm to branches of the internal iliac artery

iv.Buttock skin may be painfully swollen, cyanotic and develop gangrene

v.Painless lumbosacral plexopathy may follow cisplatin injection into the iliac artery

  1. Obstetric and gynecologic procedures that damage the lumbosacral plexus:
    1. Risk factors:

i.Short women with large babies

ii.Prima gravida

    1. Postpartum weakness:

i.Lumbosacral trunk injury (primarily L5 spinal nerve) compression at the pelvic brim over the sacroiliac joint:

1.Cephalic pelvic disproportion

2.Protracted labor

3.Mid pelvic forceps delivery

    1. Involvement of the quadriceps muscles:

i.Bilateral in 25% of patients

ii.Concomitant with an obturator neuropathy

d.Causes of peripheral femoral neuropathy:

i.Lithotomy position under anesthesia during vaginal delivery (compression under the inguinal ligament)

ii.Separation of the symphysis pubis with direct compression of the nerve by the fetal head

iii.Epidural anesthesia:

iv.Paracervical block that affects the posterior femoral nerve (pain may be delayed by several days)

v.Lumbosacral plexus compressed at the pelvic brim by a uterine leiomyoma (accelerated growth during pregnancy)

vi.Intrapelvic Schwannoma

Catamenial Neuroendometriosis

General Characteristics

1.Usually the sciatic nerve is affected but all components of the lumbosacral plexus may be involved

Clinical Manifestations (sciatic)

1.Implantation of endometrial tissue either intra-abdominally or at the sciatic notch

2.Perimenstrual pain in the buttock or posterior thigh (sciatic involvement)

3.Weakness, sensory loss and reflex changes are dependent on the lumbosacral component or the terminal nerve that is affected

Neuropathology

1.Endometrial deposits in the sciatic notch may be associated with an out-pouching of a pocket of peritoneum

2.Endometrial perineural spread from the uterus to the sacral plexus along the pelvic autonomic nerves and then distally to the sciatic nerve or proximally to the lumbar plexus

Laboratory Evaluation

1.MRI:

a.Delineates perineural spread and retrograde menstruation with peritoneal bleeding

Surgical Trauma of the Lumbosacral Plexus

  1. Laterally placed retractor blades compress the femoral nerve between the iliac and psoas muscle during:
    1. Vaginal hysterectomy
    2. Modified lithotomy position (under anesthesia)
    3. Pelvic procedures (ovarian tumors and cysts)
  2. Hip joint replacement:
    1. Approximately 0.7-1% of hip replacement surgeries are complicated by femoral, obturator or sciatic palsies
    2. Subclinical nerve damage occurs from:

i.Preoperative stretch injury due to hip dislocation

ii.Retroperitoneal hemorrhage

3. Other surgical complications:

a.Heat

b.Toxicity from methyl methacrylate bone cement

c.Direct trauma and that from retractor blades

d.Postoperative aneurysm formation

Aneurysm of the Iliac or Hypogastric Artery (Vascular Injury during Lumbar Disc Surgery)

General Characteristics

1.Surgical repair has been associated with ischemic plexus lesions

Clinical Manifestations

1.Motor, sensory and reflex deficits are evident in multiple nerves or segmental distributions in the affected extremity

2.Rectal examination reveals a firm pulsatile mass

3.Hemorrhage from an aortic, iliac or a hypogastric aneurysm may compress the femoral nerve

4.Retroperitoneal hematoma occurs from abdominal aortic aneurysm leakage that may affect the lumbosacral plexus and femoral nerve

Neuropathology

1.Neuropractic and axonometric injury occurs with compression and traction injuries

2.Neuromeric injury is primary with high impact trauma and some surgical procedures

Neuroimaging

1.Ultrasonography of the plexus

2.MRI (conventional) to evaluate the plexus and soft tissue

3.CT to evaluate the bone at the site of injury

Neoplasms of the Lumbosacral Plexus

General Characteristics

1.Occur in less than 1% of patients with neoplasms

2.Direct extension from an intra-abdominal tumor occurs in 75% of patients while extra-abdominal sites are the source in approximately 25% of patients

3.The lower sacral plexus is involved in approximately 50% of patients followed by the upper plexus in 30% and panplexopathy in 18%

4.Bilateral plexopathy occurs in 25% of patients (usually of the upper extremities by breast cancer)

5.Involvement of the sacral sympathetic nerves occurs in approximately 10% of patients

6.Less commonly plexus invasion occurs from lymph nodes, metastases or bony structures

Clinical Manifestations

1.In approximately 15% of patients lumbosacral plexopathy is the initial presentation of an intra-abdominal tumor

2.The most frequent presentation in >90% of patients is with pain in the low back, buttock, hip or thigh:

a.In 90% of patients the pain is unilateral in onset and is dull, constant aching and is rarely burning; cramping may occur in a radicular pattern

b.Exacerbation may occur at night

c.Patients find difficulty in achieving a comfortable position

d.Position of comfort is with the legs and hips in flexion if the iliopsoas muscle is involved

e.Pain is exacerbated by walking or sitting

f.A warm and dry foot (often red) may be seen if the sympathetic chain is involved

g.Pain may be present for approximately 3 months prior to the onset of other symptoms and signs

h.Weakness and sensory loss due to involvement of different plexus components is seen in most patients; sensory loss occurs in between 50-75% of patients and is most severe in patients with concomitant weakness

i.Progressive muscle weakness is diffuse and interferes with gait

j.Incontinence and impotence occur in 10% of patients due to bilateral involvement

k.Involvement of the lumbosacral trunk is associated with foot drop

l.Sacral involvement causes weakness of foot flexion and hamstring muscle involvement

m.Sensory deficits are most often unilateral

n.The patellar reflex is depressed with an upper plexopathy and the ankle jerk is depressed with sacral involvement

o.Peripheral edema occurs in 80% of patients with pan plexopathy, in 41% of patients with upper plexopathy and in 37% of patients with lower plexus involvement

p.A rectal mass is found in 43% of patients with lower plexopathy and in 25% of patients with upper plexopathy and 15% with panplexopathy

q.Straight leg raising test occurs (is positive) in greater than 83% of patients with pan plexopathy

r.Pain may be increased with Valsalva maneuvers

Neuropathology

1.Intra-abdominal tumor extension to the lumbosacral plexus occurs in approximately 75% of affected patients:

a.Tumor may invade directly

b.May grow along the connective tissue, epineurium of nerve trunks or perineural spread

2.Most prevalent tumors are:

a.Colorectal tumors (20%)

b.Sarcomas (16%)

c.Breast tumors (11%)

d.Lymphoma (9%)

e.Cervical tumors (9%)

f.Other tumors including multiple myeloma account for 37% of intra-abdominal tumors

3.Metastatic lesions are from:

a.Breast

b.Lymphoma

c.Sarcoma

d.Lung

e.Thyroid (rare)

f.Melanoma

g.Testicular

h.Multiple myeloma

4.Primary pelvic plexus tumors are:

a.Neurofibroma

b.Schwannoma

c.Sarcoma (degeneration of a benign Neurofibroma)

5.Benign tumors that affect the lumbosacral plexus

a.Dermoid of the omentum

b.Uterine leiomyoma

Laboratory Evaluation

1.Dependent on the type of underlying cancer and the extent of its involvement are increased

2.Sedimentation rate and C-reactive protein

3.Alkaline phosphatase

4.Protein electrophoresis

5.Prostate specific antigen

6.Uremia and hydronephrosis are associated with gynecologic malignancies

Neuroimaging

1.High resolution dedicated MR neurography

2.CT scan and conventional MRI are positive >80% of patients by the time of clinical presentation

3.Sacral bone involvement is often a sign of colorectal cancer

Radiation Therapy (X-RT) of the Lumbosacral Region

General Characteristics

  1. Median time to the onset of symptoms is variable; the usual is five years; in some patient, symptoms may appear 20-30 years after treatment
  2. There is no apparent relationship between the amount of X-RT and the latent period to symptoms
  3. Signs rarely occur with less that 40gy rads

Clinical Manifestations

1.Bilateral or unilateral slowly progressive leg weakness

2.Starts distally usually in the L5-S1 roots; muscle wasting and absent reflexes

  1. Numbness and paresthesia may be the presenting symptoms
  2. Mild pain as a late symptom (approximately 50% of patients; aching, burning and lancinating in character)
  3. May arrest after several years (usually five years)
  4. Often associated bowel and bladder symptomatology treatment

Neuropathology

  1. The usual cancers that are irradiated are:

a.Lymphoma

b.Testicular

c.Ovarian

d.Uterine

e.Cervical

  1. X-RT may induce:

a.Malignant nerve sheath tumors

b.Post-irradiation lower motor neuron syndrome

  1. A dose above 1 Gy effects can be seen in:

a.Schwann cells

b.Fibroblasts

c.Vascular and perineural cells

  1. Injury may occur after:

a.External beam photon therapy

b.Intestinal or intracavitary radiation implants

c.Combined photon and proton beam

  1. The effect is dose dependent:

a.Animal experiments demonstrate that the threshold dose is 20-25 Gy

b.Accumulated doses below 40gy with conventional fractionation of 1.8-2.0 Gy are considered to have a low risk of injury to nervous tissue.

  1. Late effects include proliferative endarteritis and fibrosis in the plexus and soft tissue; vascular permeability and venous exudation

Neuroimaging

  1. MRI:

a.Demonstrates thickening of the plexus with tumor and atrophy with X-RT; no enhancement with gadolinium with X-RT.

    1. Diffusivity measurements differentiate malignant lesions from irradiation injury
    2. High resolution MR neurography
  1. Ultrasonography

Laboratory Evaluation

1. CSF:

a. CSF protein may be slightly elevated

2. EMG:

a. Myokymia may be demonstrated in approximately 60% of patients

Radiation vs. Tumor invasion of the Lumbosacral Plexus

Radiation Plexopathy

  1. Insidious onset and progression:
    1. Sensory symptoms may begin at two months that may resolve after several months
    2. Presenting symptom and signs may be weakness
    3. Bilateral involvement
    4. Distal muscle weakness (L5-S1 roots)
    5. Atrophy and no enhancement on MRI; less diffusivity on DWI
    6. EMG may be normal or demonstrate myokymia and fasciculation

Tumor Invasion

1. Rapid onset and progressive course

2. Pain may be the initial symptom

3. Unilateral involvement

4. Proximal weakness (L1-L4 roots)

5. Enhancing mass on MRI (with gadolinium); destruction of bone

Post Irradiation Lower Motor Neuron Syndrome

General Characteristics

1.A heterogeneous group of syndromes has been described after irradiation of the distal spinal cord and cauda equine primarily as treatment for testicular cancer and lymphoma

2.The mean age at irradiation is 33 years of age (literature review)

3.The average irradiation dose is 5,225 cGy (range 3,000-14,600)

4.Latency between irradiation and symptom onset ranged from 3 months to 27 years

5.Also known as Post X-RT Cauda Equina Syndrome

Clinical Manifestations

1.Painless wasting and fasciculation of leg muscles

2.Most often a delayed onset from months to years after treatment

3.Mild sensory symptoms in some patients

4.A proportion of patients may develop sphincter involvement

5.Occasional periods of stability

Neuropathology

1.One autopsied patient that was uncomplicated by metastatic disease demonstrated:

a.A radiation-induced vasculopathy of the proximal spinal roots

b.Preservation of motor neuron cell bodies and the spinal cord architecture

Neuroimaging

1.Gadolinium enhancement on MRI of the cauda equine in approximately 50% of patients

Laboratory Evaluation

1.EMG:

a.Patchy motor nerve root involvement

b.Electrophysiological evaluation by magnetic stimulation:

i.Prolonged cauda equina conduction time that suggests focal demyelination of the nerve roots of the cauda equina

Medical Causes of Painful Lumbosacral Plexopathy

Diabetic Radiculoplexus Neuropathy

General Characteristics

  1. Involves the nerve roots and the lumbosacral plexus most often in a setting of diabetic length-dependent neuropathy
  2. Approximately 8% prevalence in type I and II diabetic patients
  3. Rarely the presenting feature of diabetes
  4. Often seen in Type II diabetic patients controlled by diet and oral hypoglycemic agents
  5. Most common onset is the sixth to seventh decade
  6. Rare to have concomitant nephropathy, retinopathy, or history of coma

Clinical Manifestations

  1. Hip and anterior thigh pain are often the initial presenting symptoms
  2. Leg weakness supervenes within a few days to weeks
  3. Weakness predominates in a lumbar plexus distribution that affects:

a.Hip flexion

b.Adduction

c.Knee extension

  1. Approximately 2/3 of patients have weakness in the L5 myotome: 50% are weak in the S1 dermatome in addition to the proximal muscles innervated by L1-L4 roots. L5 and S1 innervated muscle weakness may occur without involvement of proximal muscle weakness
  2. Sensory loss is common but often not noticed due to pain and weakness
  3. A small percentage of patients have neuropathy of the lumbosacral trunk
  4. Approximately 50% of patients have involvement of the autonomic nervous system that includes:

a.Orthostatic hypotension

b.Urinary dysfunction

c.Impotence

d.Constipation or nocturnal diarrhea

  1. 75% of patients have concurrent length-dependent neuropathy
  2. There may be gradual improvement of weakness over months, and the pain diminishes over weeks; proximal muscles are more likely to recover

Neuropathology

  1. Microvasculitis:
    1. Epineural and perivascular inflammation
  2. Multifocal fiber loss is demonstrated on nerve biopsy
  3. The process is frequently bilateral

Laboratory Evaluation

1.The sed rate is elevated in 20% of patients

2.CSF:

a.The protein may be elevated (120 % suggests root involvement)

3.EMG:

a.EMG and nerve conduction velocities to evaluate the level and extent of the plexopathy as well as the often concurrent length dependent neuropathy

Neuroimaging

1.MRI:

a.An early screen of the plexus to rule out other pathologies

b.If malignant infiltration is suspected, CT may be added to imaging parameters as up to 40% of patients have epidural tumor extension with possible bone involvement

Painless Diabetic Radiculoplexus Neuropathy

General Characteristics

1.Motor polyradiculoneuropathies without pain occur in diabetes mellitus

2.Women and men are equally affected; the median age range is 62 years (age range between 36-78)

3.Patients had DM for a median duration of 5 ½ years (most with type 2 DM)

4.Diabetic complications of retinopathy and nephropathy occur in approximately 20% of patients

5.Weight loss is seen in approximately 80% of patients (> 10 pounds)

Clinical Manifestations

1.Symmetrical polyradicular pattern with greater distal than proximal involvement (in contrast to canonical diabetic lumbosacral radiculoplexus neuropathy (DLRPN))

2.Proximal segments are involved to the same degree as in DLRPN

3.The upper limb is involved in approximately 80% of patients: this involvement is more widespread and severe than with classical DLPRN

Neuropathology

1.Nerve biopsies:

a.Ischemic injury and microvasculitis

b.Focal or multifocal fiber loss

c.Focal perineural degeneration or thickening

d.Epineurial neovascularization

e.Injury neuroma

f.Perivascular and vascular inflammation of small arterioles, venules and capillaries

Laboratory Evaluation

1.A minority of patients have an elevated sed rate or laboratory results suggestive of an inflammatory process

2.CSF:

a.Elevated protein with a normal cell count

3.EMG:

a.Reduced or absent upper and lower limb sensory and compound muscle action potential amplitudes

b.No temporal dispersion or conduction block

c.Mild slowing of conduction velocities and prolongation of distal and F wave latencies

d.Patchy and widespread involvement of lumbosacral myotomes by needle EMG

Idiopathic Lumbosacral Plexitis

General Characteristics

  1. Phenotype is similar to that of diabetic radiculoplexus neuropathy
  2. Lumbar plexus is more often affected than the sacral although pan plexopathies occur
  3. Age of onset is 30 months to 81 years of age.
  4. It is usually monophasic and mild but may be recurrent and have a progressive course
  5. Bimodal incidence:

a.Prior to age 20 years of age

b.Between 40-60 years of age

  1. Mild trauma, vaccination and viral illness have been reported to precede the illness in some patients
  2. Children, in general, have a monophasic course; adults may have recurrences

Clinical Manifestations

1.Abrupt onset of unilateral pain in the anterior thigh (lumbar plexitis) and posterior thigh and buttock (sacral plexitis); some patients have a more prolonged onset with recurrent bouts of pain

2.Muscle weakness is observed within 5-10 days of onset of the pain; it may progress for days to weeks; the pain resolves as the weakness supervenes

3.Muscle weakness of L1-L4 roots is most common and is associated with a positive femoral reverse SLR nerve test and absent quadriceps reflex

4.Lower plexus involvement:

a.Positive Tinel’s sign at the sciatic notch and popliteal fossa

b.Weakness of the anterior and posterior tibialis, everters of the ankle, foot flexors, and extensors

c.Absent Achilles reflex

5. The process may be bilateral

6. Recovery is often prolonged (over months) and is often incomplete

Neuropathology

1.Impaired glucose tolerance has been reported in some patients

2.Nerve biopsy demonstrates demyelination and axon loss similar to diabetic patients

3.Probable microvasculitis; possibly immune-mediated

Neuroimaging

  1. MRI:

a.To rule out compressive or invasive lesions

b.Gadolinium-enhanced lumbar and sacral roots, and trunks may be demonstrated

Laboratory Evaluation

1.EMG/NCV:

a.To delineate the location and severity of the process

2.HbA1c (must be negative)

3.Sed rate elevated in some patients

4.CSF:

    1. Slight increase in protein has been demonstrated in some patients.

Differential Diagnosis of Medical Causes of Painful Lumbosacral Plexus Lesions

Vasculitis

General Characteristics

1.Usually a necrotizing vasculitis

Clinical Manifestations

1.Develops acutely

2.Painful; weakness with fixed sensory loss

3.Progresses in a step-wise manner

4.Constitutional symptoms are associated that include:

    1. Fatigue and weight loss
    2. Associated conditions:

i.Granulomas of the respiratory tract

ii.Retinitis

iii.Purpura

iv.CNS involvement

v.Eosinophilia

    1. Specific entities:

i.Diabetic microvasculitis

ii.SLE

iii.Periarteritis nodosa

iv.Sarcoid

v.Steroid responsive lumbosacral plexopathy

vi.Wegener’s granulomatosis

Painful Infections Affecting the Lumbosacral Plexus

Abscess

1.Bacterial abscess whose origin is in the psoas or paraspinal musculature

2.Perirectal abscess:

a.Immunocompromised patients

b.Prior rectal surgery

c.Fever in association with groin, abdominal or back pain

i.Usually sciatic nerve radiation

ii.L4-S2 motor/sensory deficits

Anogenital Herpes Simplex

  1. General Characteristics:
    1. Less than 1% of women with primary anogenital infection develop plexopathy
    2. Most frequent incidence is in males with herpetic prostatitis

c.HS type 2 greater than type 1

d.The primary anogenital lesion may be on the cervix

e.Rare plexopathy with recurrent attacks

2.Clinical features:

a.Dermatomal leg weakness and sensory loss

b.Paresthesias and sensory loss in the perineum, buttocks, and posterior thigh

c.Urinary retention, constipation, and erectile dysfunction

d.Reduced tone of the anal sphincter; sensory loss in sacral dermatomes; loss of the bulbocavernosus reflex

e.May involve lower motor neurons of the sacrococcygeal plexus

f.Mild meningeal irritation

g.Symptoms and signs last 10 days to 3 weeks often with good recovery

3.Neuropathology:

a.HS type 2 > than type 1

4.Laboratory evaluation:

a.Diagnosis is confirmed by PCR

b.CSF may demonstrate a lymphocytic pleocytosis

Cytomegalic Virus

  1. Lumbosacral plexus noted in severely ill HIV patients
    1. CD4+ count of <200 mm3
  2. Severe pain, paresthesia and weakness in a wide distribution of lower extremity roots and the lumbosacral plexus
  3. Associated retinitis

Herpes Zoster

  1. L5-S1 roots most often affected

Tuberculosis

  1. Cold abscess; involves the psoas and iliacus muscle; (T12-L4 roots)
  2. Pyelonephritis:
  3. Upper > lower plexus

Appendicitis

1.Upper roots of the lumbar plexus

2.Characteristic iliopsoas spasm

3.Hyperalgesia (mechanical of the lower abdomen)

Iliacus muscle abscess

  1. Following laparoscopy
  2. Upper plexus involvement

Lyme disease

1.L5 root most often affected

Brucellosis

1.L5 root is most often affected

Syphilis

1.Dorsal root entry zone; meninges are inflamed and involve the cervical roots

2.Pachymeningitis cervicalis

3.HIV-associated

Epidural Abscess

1.Surgery

2.Catheters (anesthesia for pain)

3.Osteomyelitis

IV Drug Abuse

1.Pyogenic organisms

2.Staph aureus is most common

3.Affects the disc space (end arterial supply)

a.Severely painful (vibration of the bed causes pain)

b.Very positive meningeal stretch signs

4.MRI:

a.Involvement of both the anterior and posterior longitudinal ligaments

b.Enhancement of the disc space, the nerve roots, and the paravertebral muscle

5.Contiguous spread of infection to nerve roots from osteomyelitis is the most common route of infections

EBV Infection

1.Upper lumbar plexus involvement most commonly affected

Retroperitoneal Hemorrhage

General Characteristics

1.The lumbar plexus may be compressed within the iliopsoas muscle

2.Femoral nerve in isolation may be compressed by an iliacus hematoma or hemorrhage (trauma or retractor)

Clinical Manifestations

1.Femoral nerve involvement

a.The iliacus fascia is tighter than the psoas fascia; smaller hematomas produce femoral compression more frequently than diffuse lumbar plexopathy

2.Pain in the groin radiating to the anterior thigh and medial lower leg (primarily L3-L4 roots and the saphenous nerve)

3.Position of comfort is a flexed upper leg

4.Positive reverse straight leg raising test

5.Minimally painful Patrick’s maneuver (internal/external rotation of the upper leg)

6.Weakness of the quadriceps; loss of sensation in the femoral nerve territory; loss of the quadriceps reflex

7.Grey-Turner’s is sign in approximately 5-10 days over the costovertebral angle (purple blood breakdown products)

8.Clinical manifestations of psoas muscle hematoma:

a.Severe groin and lower abdominal pain

b.The upper leg is not usually flexed at the hip:

c.Negative reverse SLR test (forced upper leg extension)

d.Rarely hip flexion with external rotation of the leg is painful

e.No palpable hematoma; rarely a groin mass in palpable

f.Thigh adductor muscle weakness (obturator nerve)

Neuropathology

1.Iliacus and psoas hemorrhage; occur most often in anticoagulated patients

a.May be associated with an abrupt drop in hemoglobin

b.Rarely bilateral

c.Heparin has a greater incidence than coumadin; the newer anticoagulants have not yet been reported.

d.Often there is no preceding trauma

e.Most often a neuropractic nerve injury

Neuroimaging

1.Loss of the psoas shadow on a routine abdominal flat plate

2.MRI demonstrates the hemorrhage

Differential Diagnosis of Hemorrhagic Plexus Lesions

1.Athletic injury; hyperextension and avulsion of the iliacus muscle from the ileum

2.Localized blunt trauma; pelvic fracture

3.Disseminated intravascular coagulation

4.Hemophilia and other clotting disorders

5.Leukemia

6.Aneurysmal rupture

7.Anticoagulation

Immune Mediated Causes of Painful Lumbosacral Plexopathy

  1. AIDP (acute inflammatory demyelinating plexopathy) may involve the proximal plexus
  2. CIDP (distal nerve involvement to a greater degree than proximal nerve roots)
  3. Specific epitopes:
    1. GMI
    2. GalNAc-GTd
    3. Gd1b
    4. MAG
    5. SGPG
    6. Anti-sulfatide
  1. Paraneoplastic Antibodies:
    1. Anti-Hu
    2. Anti-Yo
    3. Anti-MA
    4. Anti-TA
  1. Post-vaccination
  2. Post serum infusion with anti-venoms antibody preparations

Toxins/Anesthetics

  1. Lidocaine/bupivacaine:
    1. 0.25% or greater concentration usually delivered by epidural catheter for severe neuropathic pain; demyelinating lesions of the roots
    2. Benzyl alcohol (adjuvant of anesthetics)
    3. Heroin (IV drug abuse); the adulterants may be talc or quinine to which there is an autoimmune response:

i.May have a delayed onset of symptoms and signs (1-2 days after infusion)

ii.Diffuse lower extremity pain

iii.Minimal weakness or sensory loss

iv.Pain clears prior to recovery of motor function

Ischemic Lumbosacral Plexopathy

General Characteristics

1.There is a large arterial network with collaterals in the pelvis that usually permits ligation of an internal iliac artery with no adverse effects

2.The arterial network arises from anterior and posterior divisions of the internal iliac arteries which supply blood to the sciatic nerve and the gluteal musculature

3.The inferior gluteal artery supplies:

a.A branch of the anterior division

b.The pelvic viscera

c.The lower hip

d.Back of the thigh

4.The posterior division:

a.Gives origin to the superior gluteal artery that supplies:

i.The gluteal musculature

ii.The femoral nerve

iii.Sciatic nerve roots

Clinical Manifestations

1.Bilateral ischemic lumbosacral plexopathy from chronic aortoiliac occlusion:

a.Presentation with progressive paraplegia

2.Gluteal muscle necrosis and lumbosacral plexopathy after renal transplantation:

a.Diabetic patients may be at extreme risk

b.Paraplegia has been reported following renal transplantation after ligation of the hypogastric artery

c.Lumbosacral plexopathy has been reported after dual kidney transplantation and after pseudoaneurysm of the iliac artery in transplanted patients

d.Mortality is extremely high in patients with gluteal necrosis

e.Aortic aneurysms with hypogastric artery ligation during repair may be complicated by:

i.Gluteal necrosis and pain

ii.Rectal ischemia and pain

iii.Anal and bladder sphincter dysfunction

Neuropathology

1.Atherosclerotic aortoiliac occlusion

2.Severe diabetic vasculopathy of the internal iliac arteries

3.Following pelvic vessel embolization for post-partum hemorrhage

a.May be associated with uterine necrosis

Laboratory Evaluation

1.Arteriography to evaluate the aorto0iliac circulation and to delineate aneurysm of these arteries

2.Recognition of gluteal necrosis:

a.Occurs in approximately 3% of patients following internal iliac artery embolization performed in a traumatic situation

b.Gluteal necrosis often misdiagnosed as a contusion or pressure ulcer; often extremely painful

Differential Diagnosis of Gadolinium Enhancement of the Lumbosacral Plexus

1.Carcinomatous meningitis

2.AIDP

3.CIDP

4.Arachnoiditis

5.Infections (CMV in particular)

6.Sarcoid

7.Leukemia/lymphoma

8.Tumor invasion

Differential Diagnosis of Unusual Lumbosacral Plexus Lesions

Acute Aortic Occlusion

1.Level of the lesion may be:

a.Conus medullaris

b.Cauda equina

c.Proximal nerve trunks

d.Lumbosacral plexus

2.Clinical manifestation:

a.Acute lower extremity monoplegia

Neuromuscular Choristoma

General Characteristics
  1. Rare congenital lesions
    1. Differentiated muscle intertwined with peripheral nerves and the lumbosacral plexus
Clinical Manifestations

1. Undergrowth of the affected limb

2. Primarily in the sciatic nerve:

a.Progressive neuropathy

b.Shortened atrophic limb

c.Pes cavus

3. Undergrowth of bone with hip dysphasia

Neuropathology

1. Normal differential muscle within the affected nerve or plexus

Neuroimaging
  1. Smoothly tapering fusiform enlargement of the sciatic nerve or brachial and or lumbar plexus components
  2. T1 and T2 signal characteristics of muscle:
    1. Longitudinal bands of loss of T1 and T2 signal
  3. Nerve fascicle thickening results in “coaxial cable” root presentation.
  4. Bilateral lumbosacral plexopathy after mesenteric thrombosis
  5. Lumbosacral plexopathy in the setting of pulmonary tuberculosis
  6. Lumbosacral plexopathy from an internal iliac artery pseuroaneurysm