354 - A case report of severe cervical canal stenosis with electromyography findings of myotonia with waning potentials

Friday, February 23, 2024

5:00 PM – 6:30 PM EDT

Presenting Author(s)

RO

Resa Oshiro, MD

Attending Physician
UCLA/VA Greater LA
Los Angeles, California, United States

Co-Author(s)

MJ

Michelle Jin, MD

PM&R Resident
UCLA/VA Greater LA
Los Angeles, California, United States

Co-Author(s)

HG

Harmandeep Grewal, DO

PM&R Resident
UCLA/VA Greater LA
Los Angeles, California, United States

Case Diagnosis: We present a case report of a patient with severe cervical canal stenosis (SCCS) and electromyography (EMG) findings of myotonia with isolated waning potentials, in addition to EMG findings of multilevel bilateral nerve root involvement typically seen in SCCS.

Case Description: This is a male patient in his 60s with chronic neck/arm pain, bilateral upper extremity weakness and paresthesias with SCCS at C4-C5 with myelomalacia and multilevel moderate-severe neuroforaminal stenosis. Exam was remarkable for right > left upper extremity weakness and hyperreflexia. EMG demonstrated acute and chronic neuropathic changes in the left C6 and/or C7 myotomes, right C5 and/or C6 myotomes, and chronic neuropathic changes in the left C5, right C7, and bilateral C8 myotomes. Acute neuropathic changes included fibrillation potential and positive sharp waves. Also observed were waning myotonic discharges without waxing component in the bilateral biceps brachii. Chronic neuropathic changes included large motor units and polyphasic potentials. Pt was subsequently evaluated by neurosurgery and neurology and his symptoms were determined to localize to the central nerve system and consistent with known SCCS and myelomalacia in addition to multilevel cervical radiculopathy. Normal AST, ALT, and CK further supports against myopathy.

Discussions: Waning myotonic discharges without a waxing component has been shown in rare cases of mechanical nerve root irritation in intraoperative settings and in rare cases of type 2 muscular dystrophy. We presented a case of a patient with SCCS and radiculopathy with atypical EMG findings of waning myotonic potentials, suggesting that the denervation/re-innervation process may affect muscle electric activity at the single muscle fiber level.

Conclusions:
Presence of myotonic discharge with waning potentials only may be an electrodiagnostic finding of SCCS with radiculopathy.