Single photon emission computed tomography is one of the major other imaging modalities of Lyme disease. In Lyme patients, cerebral hypoperfusion of frontal subcortical and cortical structures has been found.

• Single photon emission computed tomography (SPECT) imaging has been used to look for cerebral hypoperfusion, which indicates Lyme encephalitis.^[1]

• In Lyme patients, cerebral hypoperfusion of frontal subcortical and cortical structures has been found.^[2]
• In about 70% of late stage Lyme disease patients with cognitive symptoms, brain SPECT scans typically show a pattern of global hypoperfusion in a heterogeneous distribution through the white matter.^[3]
• This is a nonspecific pattern for Lyme disease, as a similar pattern can be observed in other central nervous system (CNS) syndromes such as HIV encephalopathy, viral encephalopathy, chronic cocaine use, and vasculitides.
• Careful history taking of the patient and serologic testing can easily rule out most of these syndromes.

• Global cerebral hypoperfusion deficits on SPECT in the presence of characteristic neuropsychiatric features of Lyme disease should raise suspicion of Lyme encephalopathy among patients who inhabit or have traveled to endemic areas, regardless of patient recall of a tick bite.
• Late stage Lyme disease can occur many years after initial infection.
• The average time from symptom onset to diagnosis in these patients is about 4 years.
• Seronegative disease can occur, and because CSF testing is often normal, Lyme encephalopathy often becomes a diagnosis of exclusion.
• Aberrant SPECT patterns are caused by cerebral vasculitis, a vasculitides. Brain biopsy is not commonly performed for these cases, as opposed to other types of cerebral vasculitis.

Template:WikiDoc Sources