2003 ID Question7
Pt with HIV on nevirapine, d4T, efavirenz. Has problem with peripheral sensory loss to light touch and reduced proprioception. What is the most likely diagnosis?
a) B12 deficiency
b) HIV myelopathy
c) drug toxicity
d) opportunistic infections
e) folate deficiency
B12 deficiency
Subacute combined degeneration - the dorsal columns, corticospinal and spinocerebellar tracts degenerate - the peripheral nerves and brain may also be affected.
Usually presents with paraesthesia of fingers and toes, the lower limbs become weak as a result of upper motor neurone lesion combined with peripheral neuropathy. Position and vibration sense is markedly impaired.
May be a glove and stocking type of anaesthesia caused by the associated peripheral neuropathy. Romberg's sign may be positive. Reflexes may be depressed or increased, depending on the degree of corticospina tract and peripheral nere involvement. Plantar reflexes are often extensor because or corticospinal tract degeneration.
Myelopathy
Spinal cord disease, or myelopathy, is present in approximately 20% of patients with AIDS, often as part of HIV encephalopathy. 90% of the patients with HIV-associated myelopathy have some evidence of dementia, suggesting that similar pathologic processes may be responsible for both conditions.
Three main types of spinal cord disease are seen in patients with AIDS. The first of these is a vacuolar myelopathy- pathologically similar to subacute combined degeneration of the cord such as occurs with pernicious anemia. Although vitamin B12 deficiency can be seen in patients with AIDS, it does not appear to be responsible for the myelopathy seen in the majority of patients.
Vacuolar myelopathy is characterized by a subacute onset and often presents with gait disturbances, predominantly ataxia and spasticity; it may progress to include bladder and bowel dysfunction. Physical findings include evidence of increased deep tendon reflexes and extensor plantar responses.
The second form of spinal cord disease involves the dorsal columns and presents as a pure sensory ataxia.
The third form is also sensory in nature and presents with paresthesias and dysesthesias of the lower extremities.
Opportunistic infections
myelopathy and polyradiculopathy seen in association with CMV infection. This entity is generally seen late in the course of HIV infection and is fulminant in onset, with lower extremity and sacral paresthesias, difficulty in walking, areflexia, ascending sensory loss, and urinary retention. The clinical course is rapidly progressive over a period of weeks
Drug toxicity
Peripheral neuropathies are common in patients with HIV infection.
The most common peripheral neuropathy in patients with HIV infection is a distal sensory polyneuropathy that may be a direct consequence of HIV infection or a side effect of dideoxynucleoside therapy.
Two-thirds of patients with AIDS may be shown by electrophysiologic studies to have some evidence of peripheral nerve disease.
Presenting symptoms are usually painful burning sensations in the feet and lower extremities.
Findings on examination include a stocking-type sensory loss to pinprick, temperature, and touch sensation and a loss of ankle reflexes. Motor changes are mild and are usually limited to weakness of the intrinsic foot muscles.
Response of this condition to antiretrovirals has been variable, perhaps because antiretrovirals are responsible for the problem in some instances.
When due to dideoxynucleoside therapy, patients with lower extremity peripheral neuropathy may complain of a sensation that they are walking on ice.
Differential diagnosis of peripheral neuropathy include diabetes mellitus, vitamin B12 deficiency, and side effects from metronidazole or dapsone.
For distal symmetric polyneuropathy that fails to resolve following the discontinuation of dideoxynucleosides, therapy is symptomatic; gabapentin, carbamazepine, tricyclics, or analgesics may be effective for dysesthesias. Some patients may respond to combination antiretroviral therapy, and preliminary data suggest that nerve growth factor may benefit some cases.
Didoxynucleotide therapy are nucleoside/nucleotide reverse transcriptase inhibitors- zidovudine, lamivudine,didanosine, stavudine.
(d4T is stavudine)
Folate deficiency does not cause neurological abnormalities ( get GI manifestations- diarrhoea, cheilosis, glossitis)
Therefore answer is c) drug toxicity