DIAGNOSIS: IDIOPATHIC LEUKOENCEPHALOPATHY
The patient received a diagnosis of idiopathic leukoencephalopathy. It was thought to be of an infectious etiology and presumed triggered by her course of corticosteroids. Her condition was considered atypical for several reasons. Her illness was milder than most cases of leukoencephalopathy. Infectious leukoencephalopathy is usually associated with severe immunosuppression (as seen with AIDS) or chemotherapeutic agents; it is rarely triggered by corticosteroids alone. It has been reported among patients treated for autoimmune conditions, such as ulcerative colitis and lupus.1
A diagnosis of leukoencephalopathy carries a poor prognosis, but reversible cases are often seen as well. Cases of posterior reversible leukoencephalopathy are more common than those involving the parietal and frontal regions, as occurred in this patient.
Conditions that must be ruled out include:
• Infectious or inflammatory encephalitis
• HIV infection
The lesions may be primary brain tumors or metastatic cancer. Some types of cancer can predispose to leukoencephalopathy by inducing immunosuppression. Infections could potentially be identified by LP or with a biopsy of the lesion.
A sudden vascular event that caused four strokes at once would require a cardiac and carotid evaluation to search for the source of an embolic shower. Cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) is vascular condition that also should be considered. With CADASIL, there should be a family history, although some patients might not have an affected family member. And while infarcts in CADASIL typically involve white matter, gray matter involvement has been reported as well.2
• Unexplained brain lesions should be evaluated with repeated brain imaging
• When a patient has several brain lesions without a clear vascular etiology, imaging the spinal cord may be necessary as well
• Solid mass infections and isolated inflammatory lesions may not always produce cellular abnormalities detected by LP
1. Kikuchi S, Orii F, Maemoto A, Ashida T. Reversible posterior leukoencephalopathy syndrome associated with treatment for acute exacerbation of ulcerative colitis. Intern Med. 2016;55:473-477. doi: 10.2169/internalmedicine.55.5250.
2. Lambert C, Sam Narean J, Benjamin P, et al. Characterising the grey matter correlates of leukoaraiosis in cerebral small vessel disease. Neuroimage Clin. 2015;9:194-205. doi: 10.1016/j.nicl.2015.07.002.