Neurology of Diabetes
CASE
A 58-year-old man comes to you because he has “burning” on the skin of his abdomen. His wife says his “belly sticks out on one side.” He has diet-controlled diabetes mellitus. He has had an extensive GI workup without any findings. His exam shows absence of superficial abdominal reflexes, with patches of sensory loss over the abdomen and thorax.
Diagnosis
Diabetic thoraco-abdominal polyradiculopathy.
Patients with diabetes frequently have neurologic symptoms. “Neuropathy” is a classic diabetic complication. Most of the neurologic complications of diabetes involve the peripheral nervous system. Cerebrovascular disease and metabolic encephalopathies caused by hypoglycemia or hyperglycemia are the most common central nervous system complications of diabetes.
DIABETIC NEUROPATHY
Distal Polyneuropathy
Distal polyneuropathy is the most common diabetic neuropathy. It presents as a slowly progressive, symmetric, distal (“glove and stocking”), predominantly sensory polyneuropathy. It is caused primarily by metabolic changes in the nerve due to chronically elevated blood sugars. Ankle jerks are generally absent, and vibration sense is diminished; pin and temperature may be decreased distally in the legs more than the arms. The loss of sensation can lead to trophic changes and injury.
Mononeuropathy
Mononeuropathy is a dramatic diabetic neuropathy that probably results from nerve infarction. The onset of motor and sensory loss in one nerve is abrupt, and often painful. The involved nerve may be tender. Prognosis is good, and recovery usually occurs in 4 to 6 months. Treatment is with physical therapy and appropriate support (splints where needed). There is a predilection for certain nerves. The most commonly affected are as follows:
Oculomotor (III) nerve. The patient has diplopia, and may have pain over the eye. There is an almost total ophthalmoplegia. (Lateral eye movement is spared.) The pupillary fibers are on the outer perimeter of the nerve, and vascular infarction occurs centrally. Thus, the pupil is of normal size and reacts to light (a pupil-sparing third-nerve palsy). A clue to a “diabetic third” is that the pupillary fibers are often spared.
Abducens (VI) nerve. There is an isolated inability to move the eye laterally. Remember, a sixth-nerve palsy may also be the first sign of increased intracranial pressure. (Check for headache and papilledema.)
Femoral nerve. There is pain in the lateral and anterior thigh, weakness and atrophy of quadriceps (extension at knee), plus weakness of iliopsoas (flexion of hip), and a diminished or absent knee jerk (see Chapter 10).
Radial nerve and peroneal nerve. There is wristdrop or foot-drop, respectively (see Chapter 10).Related posts:
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