Cognitive decline and depressed level of consciousness in AIDS : Diagnosis

Please refer to page 30 of the March 2011 issue of the SAJR (http://www. sajr.org.za/index.php/sajr/article/view/450/425) for the presentation details and radiographic images. We congratulate Dr Himal Gajjar (Schnetler, Corbett and Partners, Cape Town) for the precise diagnosis, for which he receives an award of R1 000 from the RSSA. Professor Andronikou and Dr Els elaborate below on the condition and its radiological signs.

at MRI and results in the overlying cortex being sharply contrasted with the lesion. 7ollowing CT, our patient underwent an MRI (Fig. 2), which demonstrated T2 hyperintensity in the right parietal lobe, right basal ganglia and left anterior capsula externa with mild mass effect but no contrast enhancement.Only rarely do such lesions cause mass effect.PML can be differentiated from many other demyelinating diseases by the absence of perivenous inflammation and therefore a lack of enhancement on imaging.Inflammatory PML and HIV-associated PML in the setting of immune recovery following ART may, however, show contrast enhancement.A fluctuant course and interval improvement may occur with PML. 8 In patients with AIDS, atypical presentations are common, and there may be co-existent central nervous system (CNS) pathologies that will make interpretation of studies more difficult. 6Because there is no effective treatment for PML, the prognosis is very poor, resulting in death within 2 -5 months.
Our patient was diagnosed with PML and commenced on ART.The diagnosis was based on the clinical presentation, imaging findings and polymerase chain reaction (PCR) of cerebrospinal fluid testing positive for JCV.Despite being on ART, the patient presented 2 months later with new neurological symptoms, and a follow-up CT demonstrated significant progression of the lesions (Fig. 3).

HIVE
HIV encephalopathy (HIVE) is the most frequent neurological manifestation due to a neurotrophic virus causing direct infection of the CNS.Clinically, patients present with cognitive impairment and motor abnormalities.CT may be normal or show atrophy with or without white matter (WM) lesions.WM lesions are usually bilateral, symmetric, varied in size and manifest as hypodensities.They are seen in the periventricular regions, centrum semiovale, basal ganglia, brainstem and cerebellum.The subcortical WM is spared.MR is the imaging modality of choice, demonstrating lesions of high signal intensity on T2WI and iso-intensity on T1WI.There is no enhancement after contrast administration and no mass effect. 9

Toxoplasmosis
The obligate intracellular protozoal parasite Toxoplasma gondii (reservoirs in faeces of the domestic cat) is the most common opportunistic CNS infection in patients with AIDS. 7Patients present

QUIZ CASE
with fatigue, headache, fever and chills.Confusion and drowsiness may follow with seizures, hemiparesis and coma if not treated.Toxoplasma has a predilection for the gray-white matter junction and basal ganglia.CT demonstrates single or multiple hypodense lesions with surrounding oedema and mass effect.On T1WI, the lesions are hypointense and hyperintense on T2WI.On both CT and MRI, lesions may show focal, nodular or rim enhancement. 6,8This is an important feature in distinguishing lesions from PML. Occasionally the lesions may haemorrhage, which will aid in differentiating the condition from untreated lymphoma. 7Lymphoma usually does not haemorrhage prior to treatment.Often the condition is indistinguishable from PCNSL, and the lack of ependymal spread and additional imaging with single photon emission computed tomography (SPECT) and positron emission tomography (PET) can be helpful.Toxoplasma will be negative at these modalities with lymphoma (typically lager than 2cm) being positive.MR spectroscopy will typically show elevated lactate and lipid. 7

Primary central nervous system lymphoma (PCNSL)
HIV-associated lymphoma may present with symptoms such as headache, lethargy and confusion, often with an insidious onset.Any part of the CNS may be affected, but lesions are found most frequently in the periventricular region, often with subependymal and subarachnoid spread, and can be single or multiple.Multiple lesions favour toxoplasmosis as opposed to lymphoma, while callosal involvement favours lymphoma.The lesions may show oedema and exert mass effect.CT may demonstrate hyperdense or isodense lesions.On MRI, signal is iso-or hypo-intense to gray matter on T2WI and iso-or hypo-intense on T1WI.On both CT and MRI, lesions may show enhancement which may be rim, dense homogenous or nodular in pattern.Untreated lesions typically do not show signs of haemorrhage.At MR spectroscopy, the lesions will show decreased N-acetyl aspartate (NAA) and elevated choline.Elevated lactate and lipid may also appear if the voxel is placed in the necrotic area. 7e offer the following simplified flow diagram to use when faced with a similar scenario: