Reduced and then absent tendon reflexes are consistent findings. Only the ankle reflexes may be lost during the first week of illness. At an early stage, the arm muscles are usually stronger than the leg muscles, and in a few cases, they are spared almost entirely. Facial diplegia occurs in more than half, sometimes bilaterally at the same time or sequentially over days. Other cranial nerve palsies, if they occur, usually come later, after the arms and face are affected; they are the initial signs in a variant pattern of disease as described further on. At the onset, there is no fever, and if lymphadenopathy or splenomegaly occurs, they are related to a preceding viral infection.
Disturbances of autonomic function include sinus tachycardia and, less often, bradycardia, facial flushing, fluctuating hypertension and hypotension, loss of sweating, or episodic profuse diaphoresis; one or more are common in minor form and infrequently they become pronounced or persist for more than a week. Urinary retention occurs in approximately 15 percent of patients soon after the onset of weakness, but catheterization is seldom required for more than a few days. Numerous medical complications follow in severe cases as a result of immobilization and respiratory failure, as discussed further on under “Treatment.”
The archetypical illness described in the preceding paragraphs is typically a result of the widespread inflammatory-demyelinating process within peripheral nerves. This is contrasted with an axonal form of GBS described just below.
Acute Axonal Form of Guillain-Barré Syndrome
Attention was drawn by Feasby and colleagues (1986) to an acute areflexic polyneuropathy clinically similar to typical GBS but characterized pathologically by widespread and severe axonal degeneration. In their initial report they described 5 patients with a rapid evolution of polyneuropathy and slow and poor recovery. Unlike the common form of demyelinating GBS, muscle atrophy became apparent relatively early in the axonal form (within weeks). The defining feature was the presence of numerous electrically inexcitable motor nerves and signs of extensive denervation. This finding could also signify a distal demyelinating block from which complete recovery is possible (Triggs et al). Nevertheless, most cases of abrupt and severe denervating paralysis, particularly if postinfectious, are caused by the axonal form of GBS (Ropper, 1986b).
Postmortem examinations have disclosed severe axonal degeneration in nerves and roots with minimal inflammatory changes and little demyelination, even early in the disease. Based on the deposits of complement and the presence of macrophages in the periaxonal space, a humoral antibody directed against some component of the axolemma was postulated by Griffin and associates (1995). Visser and colleagues reported similar findings in a series of acute motor polyneuropathies. The outbreaks of motor neuropathy that occur seasonally in rural China have many of the same characteristics. These cases appear to be triggered largely by C. jejuni infections. Some, but not all, sporadic instances of acute axonal GBS have been preceded by the same infection. It is noteworthy that infection with the same bacteria can also induce a typical demyelinating form of GBS.
A proportion of axonal cases, perhaps up to one-fifth, are associated with circulating antibodies to the GM1 ganglioside of peripheral nerve, and some of these reflect recently preceding infection with C. jejuni. The acronyms AMAN (acute motor) and AMSAN (acute motor-sensory axonal neuropathy) are equivalents to axonal GBS. Another variant of this illness, of which we have seen several instances, has been an acute multifocal neuropathy with electrophysiologic motor conduction block that leaves the reflexes unaltered and has high titers of anti-GM1 antibody (Capasso et al). Most experience with the generalized axonal form of GBS indicates that recovery is prolonged and incomplete.