The diagnosis of CMV infection during life is often difficult. Cultures of the CSF are usually negative and IgG antibody titers are nonspecifically elevated. Newer PCR methods prove useful here. Where the diagnosis is strongly suspected, treatment with the antiviral agents ganciclovir and foscarnet has been recommended, but, as pointed out by Kalayjian and colleagues, the CMV disease may develop and progress while patients are taking these medications as maintenance therapy.
Cryptococcal infection Meningitis with this fungus and less often, solitary cryptococcoma are the most frequent fungal complications of HIV infection. Flagrant symptoms of meningitis or meningoencephalitis may be lacking and the CSF may show little abnormality with respect to cells, protein, and glucose. For these reasons, evidence of cryptococcal infection of the spinal fluid should be actively sought with antigen testing, and fungal cultures. India ink preparations are still valuable and rapid but are not currently performed consistently and well enough in many hospitals to be entirely dependable. Treatment is along the lines outlined in Chap. 31.
Varicella zoster Cerebral infections with this virus are less common complications of AIDS, but when they do occur, they tend to be severe. They take the form of multifocal lesions of the cerebral white matter, somewhat like those of progressive multifocal leukoencephalopathy, a cerebral vasculitis with hemiplegia (usually in association with ophthalmic zoster), or, rarely, a myelitis. Encephalitis caused by HSV-1 and HSV-2 has also been identified in the brains of AIDS patients, but the clinical correlates are unclear. Shingles involving several contiguous dermatomes is known to occur in HIV with CD4 counts below 500, as in other immunosuppressed conditions. Varicella has been discussed earlier in this chapter.
Tuberculosis Two particular types of mycobacterial infection tend to complicate HIV—Mycobacterium tuberculosis and Mycobacterium avium-intracellulare. Tuberculosis predominates among drug abusers and HIV patients in developing countries, and a higher-than-usual proportion of these immunosuppressed individuals develop tuberculous meningitis. Diagnosis and treatment are along the same lines as in non-AIDS patients. Tuberculosis of the nervous system is discussed in Chap. 31.
Neurosyphilis Syphilitic meningitis and meningovascular syphilis have an increased incidence in HIV patients. Cell counts in the CSF are unreliable as signs of activity; diagnosis depends entirely upon serologic tests. It is possible that HIV causes false-positive tests for syphilis. It appears that the presence of HIV infection accelerates the transition of syphilis to later stages, including infection of the nervous system. Indeed, a category of “quaternary syphilis” has emerged that consists of an aggressive and rapidly progressive necrotizing process that causes strokes and dementia as a result of involvement of brain parenchyma and vessels. The incidence of relapse of syphilis and resistance to conventional doses of antisyphilitic medication are probably increased with HIV coinfection. It is unclear, however, if the typical tertiary forms of syphilis, general paresis and tabes dorsalis, are increased in incidence because of HIV; they may require the chronicity of meningovascular syphilis to evolve. Readers are referred to Chap. 31 and the review by Marra.
Other rare organisms, such as Bartonella henselae, the cause of cat scratch fever, are found rarely in AIDS patients and have been implicated in an encephalitis.