Case of the Month: August 2013, Page 2

Answer: B. Heroin abuse

Imaging Findings

The non-contrast enhanced CT of the brain demonstrates bilateral low attenuation lesions in the globus pallida. Corresponding MRI images demonstrate restricted diffusion and T2 hyperintensity.

Discussion


The basal ganglia are highly metabolic paired deep gray matter structures which are susceptible to a wide range of toxic insults and metabolic abnormalities.  As a result, imaging findings are often non-specific.  Location within the basal ganglia, in this case, the globus pallidus, and correlation with the available clinical and laboratory data helps narrow the diagnosis.

Metabolic disorders affecting the globus pallidus include hepatic encephalopathy, kernicterus, Wilson disease, osmotic myelinolysis, methylmalonic acidemia, hypothyroidism, and hyperalimentation. Leigh disease, Fahr disease, and Hallervorden-Spatz are neurodegenerative disorders which result in pallidal lesions.

Although carbon monoxide and cyanide are the classic toxins associated with pallidal lesions, they are also seen in up to ten percent of heroin users, either as isolated lesions, or combined with other manifestation of hypoxic/ ischemic brain injury. Lesions are usually bilateral and several case reports describe associated rhabdomyolysis, as is seen in this patient. Clinical symptoms range from dystonic to akinetic-rigid syndromes and marked reduction of spontaneous activity which may be temporarily reversed with external stimulation.

Incorrect Choices

Antipsychotics medications are a common cause of rhabdomyolysis; however, pallidal lesions are not seen. Fahr disease is a rare neurodegenerative disorder which results in bilateral basal ganglia calcifications, which are not seen in this case.  Acute methanol intoxication may result in bilateral lesions to the putamen, not the globus pallidus.


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