Clinical Summary

This 86-year-old man had a 6-month history of progressive cognitive decline, aphasia, generalized weakness, and gait instability. He had also experienced urinary incontinence, hyperphagia, and weight gain but no other GI symptoms or fever. There was no recent travel history or known immunocompromised state. His past medical history included atrial fibrillation, transient ischemic attack, osteoarthritis, and hypertension.

He presented to the emergency department on June 25 with headache, generalized chest pain, and wheezy breathing. Neurologic examination revealed GCS 11 (E4 V2 M5), nonsensical aphasia, inability to follow one-step commands, but intact brainstem reflexes and normal deep tendon reflexes. Motor and sensory assessment was limited due to poor cooperation. MRI brain revealed multifocal rim-enhancing nodular lesions, predominantly within the left temporal lobe, with additional lesions involving the deep white matter, frontal lobe, and hypothalamus, more prominent on the left. During his admission, he developed a fluctuating level of consciousness, worsening expressive aphasia, and increased gait disturbances. He became unable to ambulate or to sit upright at the bedside due to unsteadiness. He underwent a left craniectomy with image-guided biopsy of the left temporal lobe lesions.

Discussion points

1. What are the key differential diagnoses in this case considering the clinical and radiological context?
2. What are the key differential diagnoses considering the histological findings?
3. What additional tests would you order?