Peripheral mononeuropathy associated with valproic acid poisoning in an adult patient

摘要

Objective: To present the case of axillary nerve neuropathy associated with valproic acid (VPA) poisoning. Case report: A 26-year-old man was hospitalized because of a suicide attempt with VPA overdose. Toxicology analysis revealed high serum VPA level (2,896 μmol/L; therapeutic range: 350 - 690 μmol/L). Three days after admission, the patient complained of weakness in his right arm. Neurological examination revealed weakness of flexion and abduction of the right arm and loss of sensation in the skin over the lateral upper right arm. A nerve conduction velocity test was normal in the ulnar, radial, median, musculocutaneous, and suprascapular nerves. Compound muscle action potential showed reduced amplitude and prolonged latencies in the right axillary nerve taken from Erb's point and absent taken from distal stimulation point. Right axillary nerve paresis was diagnosed and the patient underwent a physical therapy program, which resulted in gradual recovery. Discussion: In the presented case, other possible causes of neuropathy were excluded by medical history, laboratory and radiological tests, and clinical course of the disease. The temporal relationship between the VPA poisoning and the occurrence of neuropathy supports the hypothesis of a VPA-caused axillary neuropathy. According to the Naranjo's Adverse Drug Reaction (ADR) Probability Scale, VPA-induced neuropathy was rated "probable". Conclusion: VPA-induced neuropathy may be a serious ADR, but it is potentially preventable and reversible. Thus, clinicians should be aware of this rare ADR.