Muscle spasms, twitches in arm upon throwing • Dx?

THE DIAGNOSIS

The patient’s FP was aware of the “yips,” a condition that is commonly viewed as psychological or related to performance anxiety. (The “yips” are colloquially known as “Steve Blass Disease”—named after a Pittsburgh Pirates pitcher who suddenly lost the ability to control his pitches.¹) But based on the patient’s clinical presentation and history of seeing a number of mental health care providers—in addition to his worsening symptoms—the FP ordered magnetic resonance imaging (MRI) of the brain. The MRI turned out to be unremarkable, so the patient was referred to Neurology.

In the general neurology clinic, a diagnosis of Wilson’s disease (a condition that leads to excess copper deposition in mul­tiple organ systems, including the nervous system) was considered, as it can cause symptoms similar to those our patient was experiencing. However, a complete blood count, complete metabolic panel, antinuclear antibody test, ceruloplasmin test, and copper level were all normal, effectively ruling it out. An MRI of the cervical spine showed mild to moderate right foraminal stenosis at C3-4 and C5-6, but this did not explain the patient’s symptoms.

A diagnosis of paroxysmal exercise-induced dystonia was also considered at the time of the initial work-up, as our patient’s symptoms were most pronounced during physical activity. But this condition usually responds to antiepileptics, and carbamazepine and phenytoin were each tried for multiple months early in his evaluation without benefit.

3 factors led to a diagnosis of focal limb dystonia: Only our patient’s right arm was affected, his laboratory and imaging work-ups were negative, and he didn’t respond to antiepileptic treatment. Characterization of a movement disorder is based upon phenomenology. In this case, the patient had sustained abnormal posturing at the shoulder during right upper limb activation, which was only triggered with specific voluntary actions. This was consistent with dystonia, a movement disorder characterized by sustained or intermittent muscle contractions causing abnormal movements and/or postures—often initiated or worsened by voluntary action.²