Case reportClinical and EEG features of acute intrathecal baclofen overdose
Introduction
Spasticity is a major problem related to spinal cord injuries. Use of intrathecal baclofen with an implanted pump seems to be a very useful therapeutic option in patients for whom oral antispasmodic agents are either ineffective or produce intolerable side effects [1]. Only a small proportion of patients develop potentially life-threatening complications of intrathecal baclofen delivery. We report a case of acute intrathecal baclofen overdose occurring after refilling of the implanted pump. We also present the clinical and electroencephalographic features of such overdose and discuss the risk of iatrogenic overdose by manipulating implanted pumps.
A 60-year-old male was admitted to our neurologic intensive care unit (neuro ICU) for respiratory distress. He had a history of spastic tetraparesis following surgery for cervical ependymoma treated with intrathecal baclofen through an implantable pump (Archimedes Implantable Constant-Flow Pump; Codman, Raynham, MA, USA). The patient was obese with a body mass index of 33 kg/m2. He was admitted to the neurosurgical ward several hours earlier for intrathecal baclofen withdrawal syndrome with increasing lower limb spasticity and myoclonia. The empty pump was refilled with 60 mg baclofen via the port. Over the next 2 h, the patient developed hypotonicity and respiratory distress requiring neuro ICU admission. On initial examination, peripheral blood pressure was 75/45 mmHg, heart rate was 80 beats/min, peripheral oxygen saturation was 85% with oxygen at 15 l/min, and initial Glasgow coma scale (GCS) score was 13 (Y3 M5 V5). While in our unit, the patient's GCS fell to 7 (Y1 M4 V2). He was orally intubated following rapid sequence induction. Arterial pressure increased after intravenous fluid challenge (500 ml 0.9% sodium chloride and 500 ml 4% gelatin) and remained stable. Baclofen overdose was immediately suspected. When we attempted to empty the infusion pump, needle aspiration retrieved only 5 ml. Consequently we estimated that the patient received 55 mg baclofen intrathecally. Aspiration of 80 ml of cerebrospinal fluid (CSF) was performed to decrease the load of baclofen. CSF analysis showed normal values for cell counts, protein, and glucose. CSF baclofen level assessed by high-performance liquid chromatography was 2062 μg/ml (normal <1000 μg/ml), confirming overdose. Serum baclofen level was detectable at a very low level (<100 μg/ml). On hospital day one, electroencephalography (EEG) showed typical continuous multifocal pseudoperiodic sharp waves (Fig. 1). The patient recovered spontaneous breathing and complete consciousness the next day and was extubated. He was discharged from the neuro ICU on day four.
Section snippets
Discussion
Baclofen is a structural analogue of the inhibitory neurotransmitter gamma aminobutyric acid (GABA) used as a muscle relaxant and antispasticity agent. It binds to presynaptic GABAB receptors within the brain stem and the dorsal horn of the spinal cord. It acts by restricting calcium influx into the pre-synaptic nerve terminal, thereby reducing the release of pre-synaptic transmitters. Baclofen mimics the inhibitory effect of GABA on spinal interneurons to alleviate intractable spasticity. When
References (11)
- et al.
Status epilepticus complicating intrathecal baclofen overdose
Lancet
(1992) - et al.
EEG changes in intrathecal baclofen overdose: a case report and review of the literature
Electroencephalogr Clin Neurophysiol
(1998) - et al.
Intrathecal baclofen overdose followed by withdrawal: clinical and EEG features
Pediatr Neurol
(2005) - et al.
Burst suppression EEG with baclofen overdose
Clin Neurol Neurosurg
(1991) - et al.
Intrathecal baclofen in the treatment of spasticity
Acta Neurochir Suppl
(2007)
Cited by (11)
Prevalence and risk factors of baclofen neurotoxicity in patients with severely impaired renal function
2020, NefrologiaCitation Excerpt :Patients with a history of seizures may have more pronounced seizures.3 If baclofen-induced acute encephalopathy occurs, an electroencephalogram is requested, in which case, the results may reveal various patterns, such as periodic 3 phase complex; however, no special treatment is required.19–22 There is no specific antidote to baclofen toxicity, and hemodialysis is most commonly used for treating neurotoxicity because of its low-molecular-weight, lipophilic nature, and low binding to proteins.1,4,7,15,23
Influence of Medication on the EEG: A Review
2022, Klinische NeurophysiologieElectroencephalography showing dying brain in a patient with acute baclofen poisoning
2017, Russian Sklifosovsky Journal of Emergency Medical CareBaclofen and clonazepam overdose in a patient with chronic neck and shoulder pain
2017, Ceska a Slovenska Neurologie a NeurochirurgieBest Practices for Intrathecal Baclofen Therapy: Troubleshooting
2016, Neuromodulation