Exacerbation of Major Depression in a Patient with a Peripheral Nerve Stimulator

Abstract

Mood disorders have been shown to influence the effectiveness of interventional treatment modalities for chronic pain. Likewise, spinal cord and peripheral nerve stimulators have been shown to improve depression scores in patients with chronic pain when effectively treating the pain. However, to our knowledge, a case of peripheral nerve stimulation worsening a patient’s depression has yet to be described. We present a case of a 62-year-old female with pre-existing bipolar disorder and left sided occipital neuralgia referred for interventional treatment. Greater occipital nerve block and radiofrequency neurotomy of the greater occipital nerve did not provide her long lasting effect. A peripheral nerve stimulator was then implanted over the greater and lesser occipital nerves. Pain relief was near 100% for four months. During this time the patient exhibited increased mood variability and worsening depressive episodes, as well as auditory and visual hallucinations. Deepening depression resulted in hospital admission for suicidal ideation, despite multiple adjustments to psychiatric medications. After ten months of worsened depression, and several adjustments to the stimulator settings, the stimulator was deactivated. Two weeks after deactivation, without changes in her medication regimen, subjective mood scores had risen dramatically with fewer episodes of suicidal ideation. Three months after deactivation, subjective grading of concentration, appetite, and mood had stabilized at much higher levels. The stimulator was ultimately explanted. Peripheral nerve stimulation has been shown to effectively treat many neuropathic pain syndromes. This case suggests a causal relationship between stimulator implantation and mood alterations. We postulate that the exacerbation of this patient’s depression may have been in part due to effective pain control. The neuropathic pain she previously experienced may have acted as a distractor that, when abolished, allowed her to focus more intently on her depression. In conclusion, peripheral nerve stimulation may negatively affect mood variability in a specific subset of patients.