In patients infected with HIV, the whole neuraxis is vulnerable to damage. Up to 10% of patients may present with a neurological disorder at seroconversion (Box 8.1).

The aseptic meningoencephalitis, which is usually self limiting, presents with headache, meningism, cranial nerve palsies and seizures. An acute demyelinating polyradiculoneuropathy (Guillain-Barre syndrome) is identical to that found in non-HIV-infected individuals, clinically and in the response to treatment with intravenous immunoglobulin or plasmapharesis.

Box 8.1 Seroconversion neurological presentations

• Encephalitis

• Aseptic meningitis

• Myelitis

• Cauda equina syndrome

• Acute demyelinating neuropathy (Guillain-Barre syndrome)

• Myositis

During the asymptomatic phase of the illness, which may be of variable duration, headache and cranial nerve palsies (especially VIIth nerve — Bell's palsy) may be the only manifestation of a low-grade chronic meningitis.

The opportunistic infections and tumours as well as the complications ascribed to HIV itself usually develops when the CD4 count drops below 200∕mm³ (Box 8.2). Since the introduction of HAART, there has been a significant reduction in the incidence of infections such as toxoplasmosis and CMV.