Carpal Tunnel Syndrome or Something Else?

CHALLENGING CASE

A 56-year-old man complains of tingling in the right hand for the past several months, and one week of pain and weakness of his right thumb and index finger. He suggests that he may have developed carpal tunnel syndrome and he explains that for the past year, he has taken up playing video games, often for hours at a time. He says that his wife has been complaining about his gaming and that he gets frustrated when he is interrupted while playing.

He reports that he is concerned he may be depressed, and he has been feeling intermittently sad for several years. He believes gaming might be a way to mask his depression. His life has been stable and enjoyable, and he says he “does not have any reason to feel sad.” He is happily married, his youngest child is in college and living at home, and his older child is married and has a steady job. The patient himself has a good job and he hopes to retire at age 65.

Past medical history is significant for Parkinson disease (PD), diagnosed five years ago, and hypertension, diagnosed eight years ago. He is prescribed pramipexole for management of his PD and verapamil for the hypertension. He also a family history of depression and anxiety.

Physical examination

The patient appears to be in good health and is alert and oriented. He has no skin lesions, rashes, or skin discoloration. He is negative for tremors or other unusual movements.

His cardiac, respiratory, and abdominal examinations were normal. His blood pressure is 120/75 and his pulse, 68 BPM. Eye examination is negative for jaundice, ptosis, or diplopia, and extraocular movements are full without nystagmus. The face appears symmetrical and facial motor movements and sensation are normal.

Neurological examination for strength is 5/5 in bilateral upper and lower extremities, with the exception of his hands. He has mild weakness in both thumbs. The arms and legs are slightly rigid on passive movement, with slight cogwheeling of bilateral upper and lower extremities.

A sensory examination is normal to all modalities, and reflexes are normal. Coordination is intact, but finger-to-nose movements are slow bilaterally. His gait is normal, and tandem walking is made without difficulty. Romberg test is negative.

Diagnostic tests

Results from electrolyte and thyroid tests are normal. Nerve conduction studies are used to assess symptoms.

What diagnosis do you suspect? >>

DIAGNOSIS: CARPAL TUNNEL SYNDROME SECONDARY TO MEDICATION-INDUCED IMPULSE CONTROL DISORDER

Nerve conduction studies reveal the patient has bilateral carpal tunnel syndrome, likely due to overuse of his hands from video game compulsion. The patient is describing possible symptoms of depression, which may be an adverse effect of his medication for PD. Gaming itself could be related to depression. He is displaying signs of impulse control disorder, which has been noted with dopamine agonists and dopamine replacement therapy.

Discussion

Most dopaminergic medications have been associated with impulse control symptoms. While this effect has not been reported among the majority of patients who use these medications, some recent studies suggest that it may be under recognized. A variety of behaviors have been described. These include stereotyped gestures, repetitive motor behaviors, compulsive gambling, and impulsive behavior.¹ There is some suggestion that this effect is more common among people who have been diagnosed with PD at a young age.

Denervation and/or sensitization of the mesolimbic system are believed to predispose patients with PD drug-induced overstimulation of dopamine receptors, producing hyperdopaminergic behavioral problems.²

Clinical management of impulse control in PD includes a number of strategies. Reducing the dosage of dopaminergic medication is often the first strategy, but symptoms of PD may not be as well controlled once doses are reduced. Antipsychotics may be used to manage symptoms in patients who do not have PD, but they have not been proven effective in medication-induced impulse control disorder. Other strategies include use of sodium valproate and deep brain stimulation (DBS).³ Unfortunately, impulse control disorders do not respond well to treatment and can have a substantial impact on quality of life in those affected.

Take home points

• A diagnosis of carpal tunnel syndrome can explain symptoms such as numbness, pain, and weakness, but the cause of overuse should be investigated, especially if it is acute.

• Behavioral changes are often considered to be effects of depression, but behavioral symptoms can result from another etiology, even in the presence of depression. All aspects of a patient’s condition should be considered before attributing behavioral changes to depression.

• Impulse control disorders can result from dopaminergic medications used to treat PD.

References:

1. Weintraub D, Claassen DO. Impulse Control and Related Disorders in Parkinson’s Disease. Int Rev Neurobiol. 2017;133:679-717.

2. Béreau M, Fleury V, Bouthour W, et al. Hyperdopaminergic behavioral spectrum in Parkinson’s disease: A review. Rev Neurol (Paris). 2018;174:653-663.

3. Warren N, O’Gorman C, Lehn A, Siskind D. Dopamine dysregulation syndrome in Parkinson's disease: a systematic review of published cases. J Neurol Neurosurg Psychiatry. 2017;88:1060-1064.