Treating Mixed Pain

Treating Mixed Pain

by Charles E. Argoff, MD

Expert authors received compensation from Janssen Pharmaceuticals, Inc. for their contributions to PrescribeResponsibly.com

Case Study Profile

  • Treating mixed pain
  • Male
  • Age 54

Situation Overview

You are seeing a 54-year-old male in your office whose chief complaint is of increasingly severe low back, bilateral knee and foot pain as well as numbness in both feet. His symptoms have been present for 3 months and are not associated with any particular event or trauma.


Scenario

His past medical history is notable for Type 2 Diabetes Mellitus known for six years, hyperlipidemia, and hypertension. In addition, he has experienced occasional nondisabling episodes of low back pain since his mid-30s and regularly exercises and stretches as part of his daily regimen. An MRI examination of his lumbo-sacral spine done 4 years ago had demonstrated multilevel degenerative joint changes, disc desiccation at the L3-4, L4-5, and L5-S1 levels but no specific disc herniations or nerve root impingement. It had been ordered by an orthopedist who subsequently recommended therapeutic exercise as a treatment. He notes as well that recently his balance is "off" and that he feels burning in his feet.

Current medications include: lovastatin, metformin, enalapril, and occasional use of ibuprofen, naproxen, or acetaminophen.

Upon examining him, you note that his blood pressure is 130/80mm Hg, HR: 72, RR: 16 Pain level: 6/10 and his BMI is 21. His general examination is otherwise unremarkable and peripheral pulses are present. Straight leg raising is negative but there is restriction of forward flexion of the lumbar spine due to increased pain, and his lower back is generally tender to palpation. Neurological examination reveals that he is alert and fully oriented with higher cortical functions intact. There are no cranial nerve deficits and his strength is full in all extremities. His sensory examination reveals diminished pin prick to the calves bilaterally, and impaired vibratory and position sense in both distal lower extremities. Monofilament testing also confirms sensory abnormalities in his distal lower extremities. His deep tendon reflexes are intact in the upper extremities and at both knees, but his ankle jerks are trace present. There are no carotid bruits noted by auscultation.


Key Learning

How does this examination help you to understand the possible etiology(ies) of his current pain complaints?

The diagnosis of chronic spinal degenerative disease has already been established. What is demonstrated on examination are new findings that are consistent with a peripheral neuropathic process. Given his history of type 2 diabetes mellitus, you suspect that he has developed a peripheral neuropathy associated with diabetes and further testing is considered, including blood work to rule out nondiabetic etiologies to his apparent neuropathy as well as electrophysiologic testing. You arrange for such testing, including an EMG/NCV of the lower extremities and blood work, and the results demonstrate a sensorimotor symmetric peripheral neuropathy, no other medical condition that would cause neuropathy other than his known type 2 diabetes mellitus and, a Hemoglobin A1C of 7.5 percent. You counsel him regarding optimizing his diabetes treatment and discuss the etiologies of his current pain complaints with him.


Application

The above represents an instance of mixed pain. Although he has a known history of a non-neuropathic type of chronic pain condition-nonradicular chronic low back pain associated with spinal degenerative changes, he has developed a neuropathic pain condition, eg, painful diabetic neuropathy. Recognizing that he is experiencing mixed pain types is vital for optimizing treatment. Pharmacologic approaches typically effective for non-neuropathic pain such as nonsteroidal anti-inflammatory drugs (NSAIDS) are not typically effective for neuropathic pain conditions such as painful diabetic neuropathy. Certain pharmacologic agents such as opioids and serotonin-norepinephrine reuptake inhibitor (SNRI) agents may be effective for both.