Abstract
Philip Reid and Saxby Pridmore, Department of Psychological Medicine, Royal Hobart Hospital, Hobart, Australia:
A 22-year-old science masters student with a 4-year history of bilateral facial pain was referred for a course of transcranial magnetic stimulation (TMS) for a concurrent major depressive episode.
She had a strong family history of facial pain. Her pain was triggered by the removal of impacted teeth in 1996. Since then, debilitating pain had persisted despite gangliotomy and the use of numerous medications including methadone, morphinesulphate, gabapentin, tramadol and amitriptyline. Her mood state was also difficult to treat with past use of venlafaxine, nefazadone and, more recently, fluoxetine. Current medication included morphine 50 mg nocte, fluoxetine 60 mg daily, gabapentin 1200 mg daily, propranolol 40 mg q.i.d. and tramadol 100 mg q.i.d., which was unchanged throughout the treatment course.
The course of TMS consisted of 14 sessions over 3 weeks and was well tolerated. Each session comprised 30 trains of 2 s at 20 Hz to the left prefrontal cortex. Stimulation was given at 100% of motor threshold. Pain intensity was monitored with the aid of a visual analogue scale, and the Montgomery and Asberg Depression Rating Scale (MADRS) and Beck Depression Inventory (BDI) measured depression at entry and exit.
In the first week of treatment, little change was noted in either her pain or depression. However, in the second week, she reported a decrease in her pain of 42%. Reduced pain reporting and behaviour was also considered clinically significant by her regular treating physicians. Her pain response had plateaued by the third week but was maintained at the 4-week follow up. In contrast, her mood did not show significant improvement over her treatment course. The MADRS moved from 27 to 19, while the BDI was static moving from 47 to 48 at exit.
Transcranial magnetic stimulation is a relatively new technology which employs the principles of electromagnetism to create electric currents in the cortex. Plastic changes have been observed in the central nervous system following administration [1]. Such change may be capable of influencing the pattern-generating mechanism of chronic pain. The present case suggests a possible therapeutic potential for TMS in chronic pain which warrants further investigation.