Prevalence and Patterns of Cranial Nerve Involvement in CIDP, Autoimmune Nodopathy, MMN, and Anti-MAG Neuropathy: A Multicenter Korea/UK study of 582 patients

Background
Cranial nerve involvement is a well-recognized feature in Guillain–Barré syndrome (GBS) but remains less well understood in chronic forms of autoimmune neuropathies. Earlier studies of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) were conducted before updated diagnostic criteria and the recognition of autoimmune nodopathy (AN), which may limit the interpretation of their findings.

Methods
We retrospectively analyzed 582 patients with chronic autoimmune neuropathies—CIDP (n = 431), multifocal motor neuropathy (MMN) (n = 64), anti-myelin-associated glycoprotein (MAG) neuropathy (n = 54), and AN (n = 33)—from 4 Korean and 1 UK centers. Patients with cranial nerve involvement were identified and described. CIDP patients with cranial nerve involvement (cranial+ CIDP) were compared with those without (cranial− CIDP).

Results
Cranial nerve involvement was observed in 8.8% (38/431) of CIDP and 24.2% (8/33) of AN patients but was absent in MMN (0/64) and anti-MAG neuropathy (0/54). Facial palsy was overall the most common manifestation (CIDP: 45%, AN: 50%). Patients with AN more frequently exhibited bilateral optic neuropathy (50%) and facial diplegia (38%), while CIDP patients more often showed trigeminal neuropathy and oculomotor nerve palsy (both 32%). Compared with cranial− CIDP, cranial+ CIDP patients were more often younger, of variant subtypes (especially multifocal), presented (sub)acutely with preceding infection/vaccination, followed by relapsing–remitting rather than progressive courses, and achieved greater improvement despite greater pre-treatment disability.

Conclusions
Cranial nerve involvement serves as a diagnostic clue in chronic autoimmune neuropathies, particularly in identifying AN and CIDP. Cranial+ CIDP appears to represent a distinct subset with partial overlap to GBS, suggesting unique underlying mechanisms.