A 40-year-old IV drug user is admitted to hospital after experiencing a first-time focal epileptic
seizure. He has a two-day history of headache, confusion, sensory aphasia, and right-sided
hemiparesis. CD4 count is 135/μL. He is on highly active antiretroviral therapy (HAART). Other
medications include trimethoprim-sulfamethoxazole (TMP-SMX). CSF analysis detects a DNA
virus. Which of the following is most likely to be seen in this patient?
- A) Multifocal subcortical hyperintense lesions on T2-weighted MRI
- B) Temporal lobe atrophy with temporopolar grey/white matter abnormalities on T2-weighted
- MRI
- C) Ring enhancing lesions on T1-weighted MRI with gadolinium
- D) Hyperintensities in the striatum or thalamus on T2-weighted MRI
0 voters
EXP:
This patient has progressive multifocal leukoencephalopathy (PML) caused by JC
polyomavirus.
PML is a CNS infection characterized by destruction of oligodendrocytes and their myelin
processes.1 It is classically seen in HIV patients with CD4 T cell counts <300 cells/mm3
.
2
The predominant neurologic manifestations are disturbance of coordination, cognitive defects, and
limb paresis.3
It is often described as causing multifocal hyperintense lesions on T2-weighted MRI. It causes
hypointense lesions on T1-weighted MRI.4, 5, 6
Yes, this sounds absurdly pedantic, but this description for whatever magical reason is HY on
the USMLE.
“Temporal lobe atrophy with temporopolar grey/white matter abnormalities on T2-weighted MRI”
(usually called “blurring”) refers to temporal lobe epilepsy.7 You do not need to know this for the
USMLE.
“Ring enhancing lesions on T1-weighted MRI with gadolinium” refers to toxoplasmosis.8 However
even if the vignette omitted telling you that a DNA virus was detected in the CSF, the fact that the
patient is on TMP-SMX makes toxoplasmosis an absolute wrong answer on the USMLE since
TMP-SMX is the prophylaxis for toxoplasmosis (and Pneumocystis jirovecii).9
“Hyperintensities in the striatum or thalamus on T2-weighted MRI” refers to Creutzfeldt-Jakob,
which is a prion disease.10 MRI is classic for T2/FLAIR hyperintensities within the basal ganglia,
thalamus, and cortex.11 You do not need to know this for the USMLE.