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Home arrow Environment arrow Inflammatory Disorders of the Nervous System: Pathogenesis, Immunology, and Clinical Management

Differential Diagnosis

HIV-associated dementia can be mistaken for opportunistic infections, CNS lymphoma, vascular disease, toxic effects, metabolic etiologies, and depression. Each one of these conditions affects the HIV patient’s cognition adversely. Meticulous examination is necessary to tease out the correct diagnosis. The patient’s age also needs to be considered as a contributing factor in the development of dementia especially as the HIV population is treated with better drugs and living longer. The differential diagnoses of HIV myelopathy include infectious, neoplastic, and metabolic myelopathies. Coinfection with varicella zoster, herpes simplex, and HTLV-I and HTLV-II should be considered and ruled out. Chronic neuropathy may be due to alcoholism, metabolic derangement, paraneoplastic, and paraproteinemic causes. cART-related neurotoxicity-induced neuropathies are dose dependent and improve with cessation.

Diagnostic Workup

Neuroimaging plays a crucial role in diagnosis, differential diagnoses, treatment, and follow-up of patients with neuroAIDS. Obtaining an MRI of the brain and spinal cord with and without contrast is of utmost significance. Patients with HIV encephalitis demonstrate cerebral and basal ganglia atrophy as well as widespread hyperintense white matter lesions on T2-weighted sequences (Fig. 3.2) [80]. 1H MR spectroscopy of patients with HAD has shown an increased myoinositol/cre- atine (mI/Cr) ratio in the frontal white matter using SV-MRS and an increased choline (Cho)/Cr ratio in the mesial frontal gray matter compared to HIV+ individuals without psychomotor slowing (Fig. 3.3) [12]. It also reveals decreased N-acetyl aspartate peak in the brain - an indicator of neuronal injury or death in the context of HAD [81]. In HIV-seropositive patients without dementia, 1H MRS reveals elevated levels of the glial marker myoinositol/creatinine in the white matter [82, 83]. Other neuroimaging findings of HAD include cerebral atrophy along with atrophy of the basal ganglia and the presence of white matter hyperintensities on FLAIR sequences. Cord atrophy may be seen on spine MR imaging which points to a diagnosis of vacuolar myelopathy.

Brain axial view, FLAIR sequence. MRS. Hyperintensity in white matter involving centrum semiovale and internal and external capsule. Widespread demyelination including the corpus callosum

Fig. 3.2 Brain axial view, FLAIR sequence. MRS. Hyperintensity in white matter involving centrum semiovale and internal and external capsule. Widespread demyelination including the corpus callosum

Magnetic resonance spectroscopy in white matter (left)

Fig. 3.3 Magnetic resonance spectroscopy in white matter (left): parietal region. On the right, frontal region. Decreased NAA indicating neuronal loss, increased myoinositol showing increased membrane metabolism corresponding to an active inflammatory process, increased myoinositol indicating increase in glial component

Examination of CSF reveals pleocytosis along with elevated protein concentration. Other reported CSF abnormalities include the detection of HIV-1 antigen as well as intrathecal generation of anti-HIV-1 antibodies and oligoclonal bands and detection of the inflammatory mediators such as CCL-2 and sCD14. Other markers of active inflammation and potent immune response in the CSF of AIDS patients include elevated levels of beta-2 microglobulin and neopterin. Bossi et al. [84] prospectively measured the level of HIV-1 RNA in the CSF of AIDS patients and reported that the HIV-1 RNA is detectable in CSF of AIDS patients; however, this parameter was not an accurate marker of HIV encephalitis. MRI and CSF examinations, combined, also enable the neurologist to exclude other differential diagnoses.

Electromyography and nerve conductions are routinely performed in AIDS patients with peripheral neuropathy. Diagnosis of AIDP and CIDP in AIDS patients follows the same protocol in HIV-seronegative patients. Certain AIDS patients with HIV-induced myopathy or muscle disease secondary to antiretroviral medications may require muscle biopsy.

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