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Prognosis in the acute motor axonal form of Guillain–Barré syndrome
  1. C M Gabriel
  1. Correspondence to:
 Dr C M Gabriel
 St Mary’s Hospital, Praed Street, London W2 1NY, UK;

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Prognosis in axonal Guillain–Barré syndrome

A primary axonal form of Guillain–Barré syndrome was first described by Feasby and colleagues1 in 1986. Initial indications were that this had a worse prognosis than demyelinating forms of the disease and it was suggested that recovery might require axonal regeneration along the entire length of the nerve fibre. In the intervening years it has become apparent that recovery from acute motor axonal neuropathy (AMAN) may actually be either rapid or slow. This is confirmed in a paper by Hiraga and colleagues (this issue, pp 719–22),2 and in addition they observed that in patients with slow recovery, clinical improvement to independent ambulation may continue for more than four years.

In the early 1990s, AMAN was characterised in northern China as a rapidly ascending tetraparesis with Wallerian-like degeneration of motor fibres at necropsy.3 This syndrome is most common in Japan and northern China, occurs uncommonly in Western countries, and is associated with Campylobacter jejuni (in 60–70%), Haemophilus influenzae (in 10–20%), and antiganglioside antibodies. Detailed ultrastructural study4 showed that the earliest changes were of myelin disruption at nodes of Ranvier, followed by macrophage extrusion into the periaxonal space at the paranode, with separation of the axon from the adjacent Schwann cell membrane, and subsequent degeneration of both Schwann cell cytoplasm and axon.

It has become clear in more recent years that although AMAN progresses more rapidly to nadir, recovery times for AMAN and acute inflammatory demyelinating polyradiculoneuropathy (AIDP) are similar, and that in fact some patients with AMAN recover more quickly,5 especially if their illness is preceded by Haemophilus influenzae. Clinically, those who recover more rapidly are equally weak at the peak of their illness, though they are more likely to retain their tendon reflexes than those with AIDP.

Rapid recovery in AMAN in the current study was defined as an improvement of two or more Guillain–Barré syndrome disability scale grades in the first four weeks e.g. from bed-bound to independent ambulation, which occurred in 27% of the AMAN group. Such improvement would be incompatible with the primary pathology being Wallerian degeneration. Other explanations might be degeneration restricted to the distal motor nerve terminal where regeneration could occur quickly, immune mediated conduction block at the axonal membrane, or complement mediated damage to perisynaptic Schwann cells. This may imply additional pathological mechanisms distinct from those described ultrastructurally by Griffin and colleagues. The authors also identified a small number of patients who were unable to walk six months after the illness but all of whom continued to improve until they could walk independently in subsequent years.

It is possible that several different pathophysiological processes exist in AMAN to explain the dichotomous recovery patterns: reversible distal nerve failure at motor terminals or conduction block at nodes of Ranvier in association with rapid recovery, and Wallerian degeneration requiring axonal regrowth which may continue over many months and years. In AIDP, conventionally considered a demyelinating condition, severe lesions may result in axonal degeneration as well as myelin destruction, and a similar distinction dependent on disease severity may occur in AMAN. Certainly there is no unifying hypothesis to date, but it is encouraging that all forms seem to be potentially reversible.

Prognosis in axonal Guillain–Barré syndrome


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  • Competing interests: none declared

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