Electroclinical Mismatch During EEG Acquisition: What It Might Mean, What We Might Need to Do

An electroclinical mismatch is present if the electroencephalogram (EEG) shows evidence of moderate to severe diffuse encephalopathy but the patient’s mental status is only mildly altered. We describe five cases in which seizure or status epilepticus was suspected due to electroclinical mismatch. In all five cases, EEG was ordered to rule out nonconvulsive status epilepticus as the cause of the altered mental status. EEG initially showed generalized delta activity (GDA), with variable degrees of rhythmicity, with or without superimposed theta activity, with or without sporadic epileptiform discharges. During EEG acquisition, all patients followed commands and answered questions. The mental status change was limited to mild inattention and temporal disorientation. Benzodiazepine challenge was performed by administering lorazepam 2-mg IV. Within 10 minutes of injection, GDA started to break up and subsequently disappeared. EEG showed prominent sleep spindles in three patients and background changes, indicating drowsiness in two patients. The assessment of clinical response to lorazepam was confounded by sleepiness in all patients. Serial EEG recording or continuous EEG monitoring revealed reemergence of GDA, at times appearing more rhythmic than the GDA in the baseline study. All patients received nonsedating antiseizure drugs. GDA completely resolved and mental status normalized two to five days after starting antiseizure medication. In cases of electroclinical mismatch, the absence of clear-cut epileptiform discharges does not exclude the possibility that cortical hyperexcitability is contributing to the encephalopathic process. A positive response to benzodiazepine challenge suggests the presence of cortical hyperexcitability and the need to start, or increase the dosage of, antiseizure drugs.

Delayed Toxic-Hypoxic Leukoencephalopathy As Sequela of Opioid Overdose and Cerebral Hypoxia-Ischemia

Delayed leukoencephalopathy in the aftermath of toxic exposure and cerebral hypoxia-ischemia is known as “delayed post-hypoxic leukoencephalopathy” (DPHL) but the name “delayed toxic-hypoxic leukoencephalopathy” (DTHL) may be more accurate if toxic and hypoxic mechanisms are both involved in the pathogenesis of delayed leukoencephalopathy. DTHL is characterized by initial recovery from toxic exposure and cerebral hypoxia-ischemia, clinical stability over a few weeks, and subsequent neurological deterioration with the sudden emergence of diffuse white matter disease. A 46-year-old man suffered respiratory failure and hypotension as a result of opioid overdose. Brain MRI showed watershed infarcts and EEG showed diffuse theta-delta slowing consistent with global cerebral hypoperfusion. He recovered fully and was discharged with intact cognitive function. Three weeks later, he presented with abulia and psychomotor retardation. MRI revealed extensive white matter hyperintensity and EEG showed diffuse polymorphic delta activity. DTHL was diagnosed based on classic MRI features, history of opioid overdose and hypoxic brain injury, and negative test results for etiology of white matter disease. He developed akinetic mutism prompting administration of methylprednisolone 1000-mg IV q24h for five days. He also received amantadine 100-mg PO q12h. His cognition, motivation, and psychomotor function slowly improved and returned to baseline about two months after the overdose. Clinic reassessment two and a half months after the overdose revealed normal cognitive function, slight residual MRI hyperintensity, and mild EEG slowing anteriorly. Toxic-metabolic myelinopathy causing diffuse demyelination in the deep white matter is a perfect explanation for the patient’s neurological symptoms, MRI changes, EEG findings, and time course of recovery.

Safety, tolerability, and pharmacokinetics of weight-based IV loading dose of lacosamide in the ICU

Among the newer antiseizure medications, lacosamide (LCM) has been increasingly used for acute seizures and status epilepticus in intensive care unit (ICU). We reviewed retrospectively weight-based dosing of IV LCM in patients admitted to ICU with acute seizures and status epilepticus. We have analyzed 354/382 patient treated with IV LCM in ICU during the years 2013-2016. Data collected were age, total body weight, body mass index (BMI), loading dose, post-IV infusion LCM blood level, duration of infusion, blood pressure, heart rate, oxygen saturation, mean arterial pressures, and documented initiation of pressor agents during or within in 30 min of infusion. Larger doses >8 mg/kg of IV LCM that can be safely administered in ICU patients produce effective plasma levels of 15-20 μg/ml with relatively constant volume of distribution.