Diabetic amyotrophy Importance of good diabetic control

Proximal skeletal muscle alterations in streptozotocin-diabetic rats: a histochemical and morphometric analysis

The response of rat quadriceps muscle fibers to chronic streptozotocin (STZ) diabetes was studied. Transverse sections of rectus femoris muscle from diabetic and weight-matched control rats were assayed for myofibrilar adenosine triphosphatase (ATPase) and nicotinamide adenine dinucleotide-tetrazolium reductase (NADH-TR). A quantitative analysis was carried out by an automatic interactive analysis system focused on the fiber type size and distribution. STZ-induced diabetes caused important effects in this muscle, with changes in the distribution of oxidative enzyme reactions, type I fiber hypertrophy, and type II fiber atrophy, which was greater in type IIB than in type IIA. It is concluded that hypoinsulinism produces morphological alterations in proximal skeletal muscle fibers that are similar to those of neurogenic myopathy. Thus the pathological changes in these mammalian muscle fibers could explain the clinical syndrome seen in diabetic patients called "diabetic symmetrical proximal motor neuropathy," perhaps the least understood of the major neuropathic complications of diabetes.

Diabetic amyotrophy: reassessment of the clinical spectrum

Diabetic amyotrophy is a syndrome whose recognition may be difficult or delayed. We reviewed thirteen patients with this disorder, all of whom had significant proximal lower limb wasting and weakness as the predominant feature and eleven of whom had pain in the affected limbs. Significant weight loss was common. In nine patients the deficits were largely or totally reversible. Important variations from the classical features were observed. Only five patients displayed asymmetric proximal lower limb wasting, weakness and pain, motor deficits in the remainder being either unilateral or bilateral and symmetrical. The shoulder girdle and arms were also involved in two patients. Proximal limb pain was not invariable, a distal sensory peripheral neuropathy was common, and diabetic control at diagnosis was likely to be good. No prognostic factors were identified. Thus, not all patients with diabetic amyotrophy exhibit the classically-described features. Other than careful clinical examination, a thorough bilateral electromyographic and nerve conduction study remains the most helpful diagnostic test. Appreciation of the clinical spectrum and context of diabetic amyotrophy should facilitate its differentiation from other disorders, including other forms of diabetic neuropathy.

Diabetic amyotrophy with primary involvement of shoulder girdle

A 64-year-old diabetic man was hospitalized for painful asymmetric wasting of the proximal muscle groups of the upper extremities. No sensory impairment was noted. Results of nerve conduction and EMG studies were normal. A biopsy specimen of the left deltoid muscle revealed thickening and hyalinization of the arterial walls with significant narrowing of the lumens and mononuclear infiltration. Diabetic amyotrophy was diagnosed despite the fact that the major muscles involved were of the shoulder rather than the pelvic girdle and that the usual simultaneous affection of the lower extremities did not occur because of the arrest in muscle wasting on achieving good diabetic control. This appears to be a unique presentation of diabetic amyotrophy. Furthermore, I believe that the muscle atrophy in this patient was not neurogenic but was secondary to diabetic angiopathy.

The syndrome of diabetic amyotrophy

Changes in the electromyograms and motor nerve conduction velocities in 12 patients with diabetic amyotrophy suggested mild distal and moderate proximal neuropathy in the lower limbs. Histological and histochemical findings in the vastus medialis muscles were consistent with denervation. Electron microscopical examination of the vastus medialis muscles in 6 patients revealed myofibrillar degeneration. One patient had abnormal mitochondria and tubular aggregates. The basement membranes of the intramuscular capillaries were thickened in all but 1 patient. Histochemical staining of the myoneural junctions showed changes consistent with degeneration and regeneration. We conclude that diabetic amyotrophy is a distinct clinical entity and is secondary to metabolic derangement rather than diabetic microangiopathy.

Diabetic amyotrophy: a follow-up study

A clinical follow-up study of 12 patients with diabetic amyotrophy is reported. Re-examination after an interval indicated that improvement had occurred in all but one instance, and had been maintained over an average follow-up period of four and a half years. Improvement in the neurological syndrome appeared to follow improvement in diabetic control or institution of treatment in those whose diabetes had not previously been diagnosed.Seven patients made a good functional recovery, three no longer having any muscular weakness. Five showed significant residual disability.