Polyneuritis cranialis—subtype of Guillain–Barré syndrome?

Recently we, along with the rest of the GBS Classification Group, outlined a new diagnostic classification system for Guillain–Barré syndrome (GBS) and Miller Fisher syndrome (MFS). This classification was based on the clinical features of each disease (Guillain–Barré and Miller Fisher syndromes—new diagnostic classification. Nat. Rev. Neurol. 10, 537–544; 2014).¹ We argued that the majority of cases could be classified into discrete subtypes of GBS or MFS—or, in some instances, overlap between subtypes—on the basis of their phenotypic appearances. There remains, however, some ambiguity as to how best classify a small subset of patients, who develop multiple, often asymmetric, cranial neuropathies in the absence of ataxia or limb weakness.

Guillain and his contemporaries^2,3 recognized that some patients developed a postinfectious syndrome that was associated with albuminocytological dissociation and affected the cranial nerves without clinical involvement of the limbs. Historically, patients with these symptoms have been referred to as having 'polyneuritis cranialis', a descriptive term that has been used in other cases of multiple cranial neuropathy regardless of aetiology. A case of polyneuritis cranialis (or isolated multiple cranial neuropathy) that was attributable to GBS was reported alongside diagnostic criteria for GBS and MFS established in 1990,⁴ but this term has not appeared in more-recent definitions^5,6 and has thus avoided nosological consideration.¹

In a recent review, we examined the clinical features of 15 historical cases of polyneuritis cranialis attributed to GBS.⁷ In the majority of cases, patients displayed a combination of ocular signs (ophthalmoplegia, ptosis or pupillary changes) and bulbar signs (dysarthria or dysphagia), which were often associated with facial weakness. Unlike other GBS subtypes, weakness was frequently asymmetric. In the absence of ataxia or cervical–brachial weakness, these patients lacked the cardinal features required to make a diagnosis of MFS or pharyngeal–cervical–brachial weakness. Furthermore, cranial neuropathy was too extensive to be attributed to any single subtype of MFS or pharyngeal–cervical–brachial weakness, and therefore a diagnosis of acute ophthalmoparesis⁸ or acute oropharyngeal palsy⁹ could not be made.

One interpretation of these cases is that polyneuritis cranialis might represent an overlap between less extensive subtypes of MFS (acute ophthalmoparesis) and pharyngeal–cervical–brachial weakness (acute pharyngeal weakness). In some patients, this notion was supported serologically by the presence of antibodies against gangliosides GQ1b and GT1a, which have also been isolated from patients with acute ophthalmoparesis⁸ and acute oropharyngeal palsy.⁹

Phenotypically, however, the majority of patients diagnosed with polyneuritis cranialis also displayed facial weakness, which has only rarely been reported in association with acute ophthalmoparesis, and not reported with acute pharyngeal weakness. Therefore, the pattern of weakness in polyneuritis cranialis extends beyond what would be predicted from the overlap between these two rare subtypes. Furthermore, facial weakness in these patients cannot be attributed to bifacial weakness with paraesthesias,¹⁰ which is caused by demyelinating neuropathy and not associated with antiganglioside antibodies. A substantial proportion of patients with polyneuritis cranialis also displayed asymmetrical neuropathy, which, although reported, occurs only rarely in patients with MFS or GBS. Given the improbability of an asymmetric overlap between two rare subtypes that are not commonly associated with facial weakness, we propose that a more plausible explanation is that polyneuritis cranialis is a separate subtype altogether, which lies at the interface between MFS and GBS (Table 1).

Table 1 Clinical features of GBS spectrum disorders