CHICAGO – Clinicians should be on the lookout for medically unexplained pain, a history of traumatic brain injury, and interictal migraine headaches in patients with epilepsy.
"These may be clinical clues to the possibility of an underlying depression in our patients with epilepsy," said Dr. Steven Schachter, past president of the American Epilepsy Society and professor of neurology at Harvard Medical School in Boston.
Depression affects 20%-55% of patients with refractory epilepsy, but it often goes undiagnosed and untreated. Screening is uncommon and depressive disorders frequently have an atypical clinical expression in patients with epilepsy. Patients may also fail to report depressive symptoms because of the common misconception that depression is a normal reaction to living with seizures, or is a part of the epilepsy itself and does not require special treatment.
There is growing evidence that depression and pain – much like epilepsy and depression – share a variety of interrelated biological pathways and neurotransmitters, said Dr. Schachter, who is also the chief academic officer at the Center for Integration of Medicine and Innovative Technology in Boston. This interaction has been called the depression-pain dyad because the two conditions frequently coexist and exacerbate each other, and may respond to similar treatments.
Dr. Schachter highlighted a review of the literature on comorbid depression and pain that cited studies in which the prevalence of pain in patients with depression ranged from 15% to 100% (mean, 65%). Conversely, the mean prevalence of concurrent depression in patients with pain complaints ranged from 13% in gynecologic clinics assessing pelvic pain to 85% among patients with facial pain in dental clinics (Arch. Intern. Med. 2003;163:2433-45).
"Given that epilepsy patients often hit their heads [and] bite their tongues, where do they fit in?" Dr. Schachter asked the audience at the Epilepsy and Depressive Disorders Conference, which was sponsored by Elsevier and its journal, Epilepsy and Behavior. (Elsevier also publishes this Web site.)
The increased likelihood of head injury during seizures and the frequent report of interictal headaches in epilepsy patients also may indicate a link between depression and epilepsy because of the high prevalence of depression in patients with migraine or traumatic brain injury, even among patients with apparently minor brain injury.
"Maybe we should think of it as an epilepsy-depression-pain triad?" Dr. Schachter posited.
There are a number of mechanisms that have been hypothesized to contribute to this triad. Perhaps the most compelling hypothesis, he suggested, is involvement of the serotonergic and noradrenergic networks that extend throughout the brain, brainstem, and spinal cord.
"Determining the underlying neurobiological alterations in pain pathways as they intersect with the neuroanatomy of depression holds a lot of promise in epilepsy," Dr. Schachter said.
The key for clinicians is to improve early identification and timely treatment of depression in patients with epilepsy. In a recent study of 8- to 18-year-old children with new-onset epilepsy, 23% had a depressive disorder and 36% had an anxiety disorder, with a striking 45% of children exhibiting Axis I disorders before their first recognized seizure (Dev. Med. Child Neurol. 2007;49:493-7). Depression may also be a factor in drug-resistant epilepsy, with patients failing to comply with their epilepsy medications because of comorbid depression, Dr. Schachter said.
Dr. Schachter reported no conflicts of interest.