Overall, the diagnosis of ALE relies on the clinical picture as a whole, combined with objective test results, which include MRI scans, EEG, and CSF testing.19 To diagnose all forms of ALE, viral and systemic autoimmune disorders are first excluded prior to examining abnormalities in objective test findings.20
EEG testing is described in the literature as being the "most sensitive tool" in making a diagnosis of encephalitis. Resp. Ex. D at 484.21 Irrespective of the type of presentation, the results of the EEG are "almost always abnormal, revealing foci of epileptic activity in one or both temporal lobes, or focal or generalized slow activity." Resp. Ex. J at 2. Specifically for ALE patients, EEG tests are "abnormal in most patients, usually showing non-specific, slow, and disorganized activity sometimes with electrographic seizures." Pet. Ex. 25N at 64. These abnormalities are generally seen in the temporal lobes of patients with limbic encephalitis. MRI findings are normal in approximately fifty percent of cases and CSF is often negative as well. Id. at 64-65.