Pathologic Alterations of Nerves

The reported prevalence of diabetic polyneuropathy varies from 5 to 80%. This unsatisfactory state may relate to evaluation of different patient groups, different minimal criteria for the diagnosis of neuropathy, and different degrees of surveillance. To made matters worse, patients with polyneuropathy tend to be equated ignoring differences in severity. To remedy this situation, four recommendations are made: (1) population-based patients should be studied, (2) nerve conduction should be used to set minimal criteria for neuropathy because the test is objective, sensitive, and repeatable, (3) validated tests of symptoms and deficits should also be used because clinical manifestations of neuropathy cannot be accurately inferred from electrophysiologic measurements, and (4) approaches to staging severity of neuropathy should be developed and used in expressing abnormality. To this end minimal criteria for the diagnosis of diabetic polyneuropathy have been proposed, and validated tests to assess neuropathic symptoms and sensory deficits have been developed. In this report we also propose a staging approach utilizing nerve conduction and neurologic history and examination and validated tests of neuropathic symptoms and deficits.

The diameter histograms of cell bodies (cytons) in motor neuron columns at the L5 segment of the spinal cord of adult man reproducibly yield three peaks of increasing height: small (Cs), intermediate (Ci), and large (Cl). Histograms of L5 myelinated axons obtained from the ventral root have two peaks of increasing height: intermediate (Ai) and large (Al). In histograms prepared from seven cases of amyotrophic lateral sclerosis (ALS), the Cl and Al peaks were decreased selectively and severely. This provides evidence for alpha, but not gamma, motor neuron vulnerability. The Cl peak of spinal ganglion neurons and the Al peak of dorsal roots were significantly reduced in number, without a concomitant increase in Ci, Cs, and Ai peaks. This, plus earlier reports of abnormal cutaneous sensation thresholds, abnormal rates of fiber degeneration in cutaneous nerves, and dorsal column demyelination, provides evidence that large afferent neurons are affected in ALS, but to a lesser degree than alpha motor neurons.