Presentation
Acutely altered mental status with fever and rapidly progressive paralysis
Patient Data
CASE OF THE MONTH: This case was selected as the Case of the Month for October 2023.
CT shows decreased density of bilateral basal ganglia and thalami. No acute territorial cortical infarction or intraparenchymal hemorrhage.
Axial FLAIR shows hyperintensity in the caudate and lentiform nuclei, thalami, substantiae nigrae, pontine tegmentum, dentate nuclei, and central medulla oblongata. There are also scattered areas of superficial FLAIR hyperintensity along the cerebellar and cerebral cortex. Geographic regions of T2 prolongation in the periventricular brain parenchyma are also evident.
DWI shows areas of mild hyperintensity in the posterior limbs of internal capsules and thalami, with corresponding ADC darkness, consistent with reduced diffusion.
These findings are concerning for encephalitis and possible meningitis.
No intracranial hemorrhage or hydrocephalus.
Sagittal MRI demonstrates T2 hyperintensity involving long segments in the cervical and thoracic spinal cord, most prominent at C3–C7 and near the conus medullaris. Corresponding axial T2 weighted images show the hyperintensity has a central grey matter and anterior horn predilection and associated cord expansion involving T10–11 to the termination of the conus. There was no abnormal contrast enhancement of the cord.
Case Discussion
This patient, with a history of extensive travel and outdoor activity, presented with acute-onset altered mental status and rapidly progressing paralysis. Cranial nerve assessment revealed reactive pupils but dysconjugated gaze and an absent bilateral corneal reflex. Motor examination indicated increased tone in bilateral lower extremities compared to upper extremities, with no spontaneous movement or response to noxious stimuli.
CSF analysis:
colourless and clear
protein 124 mg/dL
white blood cells 82 per μL (45% lymphocytes, 10% neutrophils, 29% monocytes); red blood cells 106 (tube 1) to 5 (tube 4) per μL
glucose 59 mg/dL
West Nile virus (WNV) IgM positive, WNV PCR negative
markers for other infectious agents like poliovirus, coxsackievirus, and flavivirus were negative
myelin oligodendrocyte glycoprotein antibody (MOGAD) marker was also negative
Differentials:
The patient clinically presented with acute flaccid myelitis and encephalitis. The imaging findings were consistent with longitudinally extensive transverse myelitis with grey matter predilection and encephalitis. This picture raised the differential diagnosis of enterovirus infection, flavivirus infection, and autoimmune demyelination, especially myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD).
Within the enteroviruses, there have been cases of acute flaccid myelitis or rhombencephalitis due to enteroviruses D68 and A71, primarily in the pediatric population. Within the flaviviruses, typical entities include the West Nile virus, the Powassan virus, the St. Louis encephalitis virus, and the Japanese encephalitis virus.
With positive WNV IgM and no positive associations with remaining infectious conditions, West Nile virus encephalomyelitis was confirmed as the diagnosis.
Additional author: Francis Deng, MD
Unable to process the form. Check for errors and try again.