Physician The Ohio State University Wexner Medical Center Columbus, Ohio, United States
Case Diagnosis: Cervical Myelopathy
Case Description: A 65-year-old male presented for electrodiagnostic evaluation for hand weakness. He reported 3 weeks of worsening extremity weakness, gait ataxia, and impaired hand relaxation. He was hyperreflexic with bilateral Hoffman sign and significantly impaired active finger extension. Bilateral upper limb strength and finger extension was notably worsened with neck extension. Sensation to light touch and pinprick was diminished in a length dependent fashion. Needle EMG demonstrated bilateral symmetrically reduced recruitment with slightly large, polyphasic motor units in all tested muscles. Spontaneous activity could not be fully assessed due to impaired relaxation. Paraspinal EMG demonstrated one isolated prolonged myotonic discharge that was not repeatable and multiple CRDs. Urgent cervical MRI demonstrated congenital spinal canal stenosis with superimposed posterior osteophyte complex formation and ligamentous infolding causing severe canal stenosis at C3-4 with acute on chronic cord compression and signal change. He subsequently underwent posterior cervical decompression and fusion.
Discussions: Myotonia is delayed muscle relaxation after activation from increased excitability of muscle fibers resulting in repetitive discharge of action potentials. Clinical myotonia classically improves whereas pseudomyotonia worsens with repeated muscle activation. This patient demonstrated pseudomyotonia with impaired finger extension after forceful voluntary hand contraction. His impaired finger relaxation worsened with repeated efforts and cervical extension, improved with cervical flexion and extended periods of muscle rest. This is presumed secondary to maladaptive reorganization of the corticospinal tracts due to injury.
Conclusions: Classically, pseudomyotonia is characterized as delayed muscle relaxation after contraction without myotonic discharges on EMG. While this patient exhibited one myotonic discharge on paraspinal needle study, it was not repeatable within the muscle or in other muscle groups. Pseudomyotonia is rarely associated with cervical myelopathy but should be in the differential when physical exam and needle EMG demonstrates signs of impaired relaxation. It may also be a sign of chronic spinal cord compression.