The most characteristic syndrome affects the lumbar roots. Pain, which can be severe, begins in the low back or hip and spreads to the thigh and knee on one side; the discomfort has a deep, aching character with superimposed lancinating jabs and there is a propensity for pain to be most severe at night. Weakness and later atrophy are evident in the pelvic girdle and thigh muscles, although the distal muscles of the leg may also be affected. The weakness can progress for days or weeks (rarely, months). The patellar reflex is lost on the affected side. Curiously, we have found the opposite patellar reflex to be absent in some patients, without explanation. Deep and superficial sensation may be intact or mildly impaired, conforming to either a multiple nerve or multiple adjacent root distribution (i.e., L2 and L3, or L4 and L5). The pain lasts for several days and then gradually abates. Motor recovery is the rule although months and even years may elapse before it is complete. The same syndrome may recur after an interval of months or years in the opposite leg. The EMG shows denervation in the lumbar and sometimes adjacent myotomes.
This form of neuropathy has been referred to as diabetic amyotrophy, a term that draws attention to one facet of the syndrome. Garland’s name (also Bruns’s) has been attached to this diabetic lumbar radiculoplexopathy based on his thorough report (but he mistakenly attributed the condition to a spinal cord lesion). Clinical experience has shown that an identical painful lumbofemoral neuropathy may develop in nondiabetics; possibly this form is also vasculopathic or vasculitic. While lumbar disc herniation, retroperitoneal hematoma compressing upper lumbar roots, carcinomatous meningeal seeding, and neoplastic and sarcoid infiltration of the proximal lumbar plexus enter into the differential diagnosis, the diabetic type is usually so distinctive as to permit recognition on clinical grounds alone. In an informative reexamination of this syndrome, Barohn and colleagues (1991) point out that there is considerable overlap between the chronic polyneuropathy of diabetes and this rapidly evolving regional disorder. They also point out a high incidence of involvement of the L5 root, but we find this difficult to reconcile with the frequent finding of hip flexor and quadriceps weakness in our patients. As with the diabetic mononeuropathies, the upper extremities are only rarely affected by this process.
Also observed in diabetic patients is a relatively painless syndrome of proximal symmetrical leg weakness, wasting, and reflex loss of more insidious onset and gradual evolution as discussed by Pascoe and colleagues. The iliopsoas, quadriceps, and hamstrings are involved in varying degrees. The muscles of the scapulae and upper limbs, usually the deltoid and triceps, are affected less frequently. Sensory changes, if present, are distal, symmetrical, and usually mild.
In an attempt to delineate these types of proximal diabetic neuropathies, it must be emphasized that they overlap and that distal parts of a limb may be involved to a mild degree and the evolution of symptoms varies. Whether the proximal and distal syndromes should be distinguished on pathologic or electrophysiologic grounds is not clear.