Deep brain stimulation reduces PD pain severity but does not prevent it

By Lucy Piper, Senior medwireNews Reporter

Subthalamic nucleus deep brain stimulation (STN DBS) has a beneficial effect on pain severity in patients with Parkinson’s disease (PD) that persists for up to 8 years, say researchers, but new onset of musculoskeletal pain in many suggests its effects are not enduring.

Researcher Beom Jeon (Seoul National University Hospital, Chongno-gu, South Korea) and co-workers studied the effects of STN DBS in 16 (67%) of 24 patients with PD who experienced pain when not taking their medication.

Pain was most commonly felt in the lower extremities and central pain was the most prevalent subtype. On average, the patients rated the severity before surgery as 6.2 out of a possible 10, which decreased to 3.5 at 8 years after surgery.

Off-state central pain improved or disappeared in all the patients, with the number of body parts affected reducing from 21 to 11 after 8 years.

However, the researchers note in JAMA Neurology that new pain, predominantly musculoskeletal, developed in 18 (75%) of the 24 patients, including five who had no pain at baseline. The number of body parts with newly developed pain was 47, affecting primarily the lower extremities. The patients gave an average pain severity rating of 4.4.

Jeon and team say that musculoskeletal pain, which was characterised by aching and cramping sensations in the joints or muscles, was worsened by immobility, in turn promoting immobility and aggravating parkinsonian motor symptoms.

“The results of the present study highlight once again that musculoskeletal problems should be considered when predicting the operative outcome before surgery, and continuous evaluation and treatment of musculoskeletal pain should be performed before surgery”, they say.

In a related editorial, Pravin Khemani and Richard Dewey, from the University of Texas Southwestern Medical Center in Dallas, USA, agree that the findings “direct our attention to the fact that musculoskeletal pain may emerge years after [deep brain stimulation], warranting individualized treatment”.

They say that “[a]lthough there is a growing consensus that STN DBS decreases the level of pain in people with PD, the literature is mixed on the subtypes of pain that are responsive to DBS”, adding: “For now, we have learned that STN DBS does not take the ouch out of PD in the long run.”

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