Q. You are asked to consult on a 32 year-old woman with a long-standing history of headaches and seizures who presents with profound confusion and disorientation. Her first seizure was at the age of five years old and they now occur intermittently, despite antiepileptic drug therapy. Her headaches remain frequent. She has been noted to have complained of worsening weakness over the past 10 years. Her past medical history is notable for diabetes mellitus and hearing loss. Her vital signs are normal. On general exam, you appreciate that she is of short stature. On neurological exam, you identify that she has severely compromised visual field detection. Serological testing demonstrates an elevated lactate to pyruvate ratio. Noncontrast head CT demonstrates basal ganglia calcifications. You order an MRI. A single T2 slice from the MRI is shown below. Which of the following would be most helpful to confirm the suspected diagnosis?