Anesthetic management of a patient with spinal muscular atrophy type III associated with trismus

Nao Yamamoto, Kentaro Mizuta, Eiji Masaki

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Spinal muscular atrophy (SMA) is a rare genetic disease attributable to the degeneration of anterior spinal motor neurons, causing skeletal muscle atrophy and weakness. We report the successful anesthetic management of a patient with SMA using a fiber optic intubation technique while the patient was conscious. A 26-year-old woman (weight, 48 kg ; height, 147 cm) with SMA type III was scheduled to undergo temporomandibular joint arthrocentesis and a third molar extraction under general anesthesia. The patient's mouth opening was less than 20 mm because of mandibular ankylosis, and she had severe scoliosis leading to a restrictive ventilatory impairment. Because of an SMA-related increase in sensitivity to nondepolarizing neuromuscular blockers and the prolonged effects of these blockers as well as the presence of trismus, a nasal fiber optic intubation while the patient was conscious and under remifentanil-midazolam sedation was planned. The intubation was successful, and general anesthesia was induced and maintained with propofol. Since the surgeon requested the intravenous administration of a muscle relaxant so as to determine the cause of the trismus, a small amount of rocuronium (5 mg) was administered, resulting in a repetitive train-of-four (TOF) ratio of 0%. After the completion of the surgery, the effect of the muscle relaxant was reversed with the intravenous administration of sugammadex (150 mg), with a TOF ratio of 100%, and her trachea was extubated. This case report suggests that the fiber optic intubation technique performed while the patient is conscious and under short-term sedation, such as remifentanil-midazolam sedation, could be useful for patients with trismus caused by SMA type III. In addition, anesthesiologists should take into account the hypersensitivity to nondepolarizing neuromuscular blockers, the effects of which can be reversed using sugammadex.

Original languageEnglish
Pages (from-to)183-185
Number of pages3
JournalJournal of Japanese Dental Society of Anesthesiology
Issue number2
Publication statusPublished - 2016


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