Track: 3. Neurophysiology / 3B. ICU EEG
Southern Illinois University
Baclofen is a muscle relaxant prescribed for the treatment of spasticity and trigeminal neuralgia. It produces its effects by activating the GABA B receptors. It acts primarily at the spinal level but with high doses, it penetrates the blood-brain barrier and can cause side effects, toxicity is associated with a wide range of symptoms from dizziness and confusion to CNS depression, and coma with loss of brainstem reflexes, this is associated with different EEG patterns including burst suppression. We conducted a systematic review to describe EEG changes associated with Baclofen toxicity.
We reviewed EEG findings and clinical presentation of all reported cases with baclofen toxicity and altered mental status.
We searched for articles describing EEG findings in baclofen toxicity from 1989 to June 2020 using the PubMed and EMBASE databases including retrospective studies, case reports and case series. Search terms included Baclofen toxicity, EEG, Encephalopathy, Seizures, myoclonus, and Burst suppression. From 42 articles reviewed only 18 were included, we also added the findings of one case we had seen at southern Illinois University. A total number of 61 patients were included in this systematic review. We reviewed demographic data, clinical presentation and EEG characteristics.
Patients had a median age of 48 years, 66% were males and 34% were females. All patients had altered mental status. Generalized periodic discharges (GPDs) with triphasic morphology was the most common EEG finding (36%) followed by burst suppression pattern (31%). Generalized epileptiform activity was seen in 19% of patients, while focal epileptiform activity was seen in another 14%. Forty-three percent of patients had reported clinical seizure activity, of which 52% had tonic clonic activity, 30% had myoclonus and 18% had both including our patient.
Patients with burst suppression pattern usually received more than 200 mg of baclofen and they presented in deep coma with absent brain stem reflexes. Prognosis is good and patients typically recovered clinically within two to five days after discontinuation of baclofen.
There were five reported cases of intrathecal baclofen toxicity, all with reported motor seizure activity.
Baclofen can be used as recreational drug. Baclofen overdose whether intentional or not can result in seizures, myoclonus, deep coma with absent brain stem reflexes and burst suppression pattern, and NCSE in EEG, in the absence of hypoxic and metabolic causes it is important for clinicians to recognize clinical presentation and suspect baclofen toxicity. Baclofen should be discontinued, a serum level should be drawn if possible, and serial EEGs should be done for diagnosis and follow up.