Friday, September 16, 2011

Neurologic presentations of HIV infection

Last week in morning report was an excellent case of ptosis and diplopia in a patient with HIV infection. This is a big topic, but a few points about neurologic involvement in HIV:

1) Acute seroconversion reactions: 

-Although rare, acute neurologic presentations at the time of HIV infection do occur, including aseptic meningitis, Bell's palsy, and inflammatory neuropathies. CSF testing for HIV may be positive in these patients.

2) Opportunistic infections: A variety of OI can manifest with neurologic presentations:

- Progressive Multifocal Leukoencephalopathy (PML): a demylenating CNS disease caused by JC virus, mostly in patients with CD4 counts less than 100. Usual presentation is a subacute deterioration in mental status with possible focal neurologic signs/symptoms, with fever and headache not usually present.

- Cytomegalovirus (CMV): although 60% of the population have evidence of exposure to CMV, patients with HIV and CD4 counts less than 50 and other immunocompromised states are at risk of clinical disease from reactivation. CMV can infect and reactivate throughout almost the entire spectrum of the CNS and PNS- from the brain to peripheral nerves. For this reason, the neurologic presentation can be any combination of encephalitis, ventriculitis, myelitis, gangionitis and peripheral polyneuropathy. 

- Cryptococcus neoformans: an encapsulated yeast found throughout the world. It usually is cleared by the immune system, but in immunocompromised patients, including HIV patients with CD4 counts less than 100, it can remain in a latent state that can disseminate to organs, with the CNS being particularly common. The usual presentation is that of a subacute menigoencephalitis, with fever, headache and malaise. It can also present with complications of increased ICP, including seizure.

- Toxoplasma gondii: intracellular protazoan with high seroprevalence in the population, with most primary infections being asymptomatic or flu-like. Reactivation can occur in immuno compromised hosts, usually in patients with HIV and CD4 counts less than 200. Usually casues an encephalitis and presents with fever, headache, and focal neurologic signs or seizures. 

3) Neoplasms: primary CNS lymphoma is usually a high grade B-cell lymphoma and almost always related to Epsetin -Barr Virus (EBV). It usually presents in HIV patients with CD4 counts less than 100 with headache, changed mental status, focal neurologic signs or seizures. 

4) Immune reconstitution inflammatory syndromes (IRIS): a group of syndromes casued by the inflammation generated by a reconstituted immune system in the first 4-8 weeks after starting on combined antiretroviral therapy. Usually seen in HIV patients with CD4 counts less than 50 being started on therapy for the first time in the setting of an opportunistic infection. Typically presents as a paradoxical worsening of course in patients with HIV encephalitis, cryptococcal meningitis  toxoplamsamosis encephalitis and PML.

5) HIV associated peripheral neuropathies: many peripheral neuropathic syndromes have been reported in the context of HIV infection, with the most common being a distal peripheral sensory neuropathy. Modifiable risk factors include use of neurotoxic medications, diabetes and alcohol abuse.

6) HIV-associated vacuolar myelopathy: an entity of unclear pathophysiology affecting the spinal cord neurons, more often the dorsal column. It presents with often initial errectile dysfunction and hyper-refexia, but progresses to asymmetric spastic leg weakness, dorsal column vibration/position sensory loss, and ataxic gait.

7) HIV Associated neurocognitive disorders (HAND): this is a group of neurocognitive changes thought to be a spectrum of a subcortical process that primarily affects attention/concentration, psychomotor speed, memory/learning, information processing, and executive function, while language and visuospatial abilities are often relatively unaffected.

More on diagnosis of these conditions from a review article here.

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