Transorbital sonography in CIDP patients: No evidence for optic nerve hypertrophy

Chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) is an acquired, chronic progressive or relapsing immune mediated disorder of the peripheral nervous system. Thickening of cranial nerves as a sign of central nerve involvement is increasingly reported in the last years. Our aim was to assess systematically for the first time the frequency of optic nerve hypertrophy in patients with CIDP by means of transorbital sonography (TOS). Thirty-four optic nerves of 17 patients with CIDP (age=60.8±13.3y, range=39-82y; 7 female) were examined by TOS. The diameter of Optic nerve (OND) as well as the intern and extern diameters of the sheath (ONDSi, ONSDe) was measured 3mm behind the optic disc. Findings were compared to the data of 15 healthy controls. CIDP-patients showed a mean OND of 2.8±0.4mm, an ONSDi of 4.7±0.7mm, and an ONSDe of 6.3±0.9mm. No papilledema was detectable. There was no significant difference to the healthy control group. Our study revealed no evidence for a frequent optic nerve involvement in CIDP. Reported cases seem to represent exceptions. Transorbital sonography could be a useful tool in these rare cases with optic nerve hypertrophy.