Variants of Guillain-Barré Syndrome (Table 43-3)
Portions of the typical clinical picture of GBS appear in isolated or abortive form and are a source of diagnostic confusion. Whereas in most patients the paralysis ascends from legs to trunk, to arms, and then to cranial regions, and reaches a peak of severity within 10 to 14 days, the pharyngeal-cervical-brachial muscles may be affected first or constitute the entire illness, causing difficulty in swallowing with neck and proximal arm weakness (Ropper, 1986a). Ptosis, often with ophthalmoplegia, may be added. The differential diagnosis then includes myasthenia gravis, diphtheria, and botulism and a lesion affecting the central portion of the cervical spinal cord and lower brainstem.
A syndrome comprising partial or complete ophthalmoplegia with ataxia and areflexia represents a variant of GBS described by Fisher (and is called Fisher syndrome). A purely ophthalmoplegic form also exists; it may be coupled with the pharyngeal-cervical-brachial pattern mentioned earlier. Ophthalmoplegia, whether occurring alone or with weakness or ataxia of other parts, is almost uniformly associated with a specific antineural antibody, anti-GQ1b. The ophthalmoplegic pattern raises the diagnostic possibilities of myasthenia gravis, botulism, diphtheria, tick paralysis, and basilar artery occlusion. Bilateral but asymmetrical facial and abducens weakness coupled with distal paresthesias or with proximal leg weakness is one of several other variants in our experience (Ropper, 1994). The tendon reflexes may be absent only at the ankles or at the knees. Lyme disease and sarcoidosis are then considerations in diagnosis. Whether bifacial palsy alone represents a variant of GBS is uncertain, but almost every case in our experience has had an alternative explanation.
Paraparetic, ataxic, and purely motor or purely sensory forms of the illness have also been observed. Less difficulty attends the correct diagnosis of GBS if paresthesias in the acral extremities, progressive reduction or loss of reflexes, and relative symmetry of weakness appear after several days. The laboratory tests, particularly nerve conduction studies that affirm the diagnosis of typical GBS, give similar but generally milder abnormalities if they are carefully sought in all these variant forms. In a few patients, the weakness continues to evolve for 3 to 4 weeks or longer. From this group, a chronic form of demyelinative neuropathy (CIDP) may emerge and an intermediate group that progresses for 4 to 8 weeks and then improves can be identified (see further on).