[A case of amyotrophic lateral sclerosis complicated by syringomyelia associated with Chiari type I malformation].

The patient was a 78-year-old woman. She underwent foramen magnum decompression for syringomyelia associated with Chiari type I malformation, which had developed with difficulty in raising the left upper limb and muscle weakness in both upper limbs. One year after surgery, weight loss of 20 ‍kg, progressive muscle atrophy and weakness in the extremities, paralytic dysarthria, and fasciculation in the bilateral anterior thighs were observed, and needle electromyography showed acute denervation and chronic denervation in the medial vastus muscle. The rapid postoperative progression of symptoms and lower motor neuron symptoms in the lower extremities could not be explained by syringomyelia associated with Chiari type I malformation and were considered a possible complication of amyotrophic lateral sclerosis (ALS). It is possible that the surgery may have caused ALS progression, and attention to the rate of progression of neurologic symptoms may be important in the diagnosis of ALS complications.