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Single photon emission computed tomography (SPECT) imaging has been used to look for cerebral hypoperfusion indicative of Lyme encephalitis in the patient. Although SPECT is not a diagnostic tool itself, it may be a useful method of determining brain function.

In Lyme disease patients, cerebral hypoperfusion of frontal subcortical and cortical structures has been reported. In about 70% of chronic Lyme disease patients with cognitive symptoms, brain SPECT scans typically reveal a pattern of global hypoperfusion in a heterogeneous distribution through the white matter.

 This pattern is not specific for Lyme disease, since it can also be seen in other central nervous system (CNS) syndromes such as HIV encephalopathy, viral encephalopathy, chronic cocaine use, and vasculitides. However, most of these syndromes can be ruled out easily through standard serologic testing and careful patient history taking.

The presence of global cerebral hypoperfusion deficits on SPECT in the presence of characteristic neuropsychiatric features should dramatically raise suspicion for Lyme encephalopathy among patients who inhabit or have traveled to endemic areas, regardless of patient recall of tick bites. Late disease can occur many years after initial infection. The average time from symptom onset to diagnosis in these patients is about 4 years. Because seronegative disease can occur, and because CFS testing is often normal, Lyme encephalopathy often becomes a diagnosis of exclusion: once all other possibilities are ruled out, Lyme encephalopathy becomes ruled in. Although the aberrant SPECT patterns are caused by cerebral vasculitis, a vasculitide, brain biopsy is not commonly performed for these cases as opposed to other types of cerebral vasculitis.

Abnormal magnetic resonance imaging (MRI) findings are often seen in both early and late Lyme disease.  MRI scans of patients with neurologic Lyme disease may demonstrate punctuated white matter lesions on T2-weighted images, similar to those seen in demyelinating or inflammatory disorders such as multiple sclerosis, systemic lupus erythematosus (SLE), or cerebrovascular disease. Cerebral atrophy and brainstem neoplasm has been indicated with Lyme infection as well.

Diffuse white matter pathology can disrupt these ubiquitous gray matter connections and could account for deficits in attention, memory, visuospatial ability, complex cognition, and emotional status. White matter disease may have a greater potential for recovery than gray matter disease, perhaps because neuronal loss is less common. Spontaneous remission can occur in multiple sclerosis, and resolution of MRI white matter hyper-intensities, after antibiotic treatment, has been observed in Lyme disease.

From Wikipedia, the free encyclopedia

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