A 30 y.o. male with no medical history presents for memory loss. He reports his short term memory has been gone for two weeks.

What could be wrong?

Increased T2 signal is seen in subcortical areas of the frontal lobes on MRI

Our patient had encephalitis. This inflammation of the brain or meninges has many causes including viral and autoimmune. Viral causes include mosquito-borne illness as well as tick borne. RMSF is comon in Missouri but that was not the cause of our patients disease.

Rocky Mountain spotted fever

VIRAL ENCEPHALITIS

Varicella-zoster, Epstein-Barr virus,  CMV, measles, mumps.  Can present with  rash, lyphadenopathy, hepatosplenomegaly or parotid enlargement.

St. Louis encephalitis( mosquito borne) can present with movement disorders, dysuria and pyuria.

West Nile encephalitis( mosquito borne) can present with extreme lethargy or flaccid paralysis.

Tick borne encephalitis is an important infectious disease in Europe, the former Soviet Union and Asia. Powassan virus causes tick borne encephalitis in the US.

Rabies, Zika,  HIV, and enteroviruses also can cause encephalitis.

Any viral encephalitis can present with behavioral changes, SIADH, memory disturbance or seizures

Powassan encephalitis is also tick borne and not the cause of our patients disease..

AUTOIMMUNE ENCEPHALITIS

NMDA receptor encephalitis-40% are associated with ovarian teratomas

Leucine-rich glioma inactivated 1 and contactin-associated protein 2.

Anti-aquaporin-4 is associated with neuromyelitis optica.

HIV.

Different parts of the brain can be affected by encephalitis.  Limbic system involvement may result in psychosis.  Brainstem involvement may result in cranial nerve findings. Neuromyelitis optica may result in blindness. Our patient had primarily frontal lobe involvement with his encephalitis and therefore executive function; calculation and memory were affected.

Our patient had encephalitis caused by HIV.  He had a CD4 count of 90 and was started on bicegravir-emtricitabine-tenofovir and Bactrim. His JC virus in csf was negative .  The current diagnosis is HIV encephalopathy since infectious studies were negative.  

Remember West Nile as a possible cause of encephalitis

Davidson M, Williams H, Macleod J.  Louping ill in man: a forgotten disease. Journal of Infection 1991;23(30:241-49.

Ebel G. Update on Powassan virus: emergency of North American  tick-borne flavivirus . Annual Review of Entomology.  2010;55:95-110.

DubeyD, Pittock S, Kelly C, et al. Autoimmune encephalitis epidemiology and a comparison to infectious encephalitis. Ann Neurol. 2018;83(1):166-177.