Prevalence of Decreased Corneal Sensation in Patients With Chronic Inflammatory Demyelinating Polyneuropathy

INTRODUCTION The prevalence of CIDP ranges from 0.8 to 8.4 per 100 000.5 This broad range may reflect the use of different diagnostic criteria, as recently confirmed by an epidemiologic study on UK population. Over 50% of the patients may have temporary severe disability during the course of their disease and approximately 10% eventually become persistently disabled or die because of the illness.

CIDP may affect any nerve plexus in the body. However, diagnostic criteria leans towards nerve conduction studies in the limbs and denervation in other organ systems might be overlooked. Sensory innervation of the cornea is provided by the ophthalmic branch of the trigeminal nerve via the anterior ciliary nerves. A relatively small number (50-450) of primary sensory neurons from the ipsilateral trigeminal ganglion send their peripheral axons to the cornea and branch extensively within the corneal tissue. To maintain corneal transparency, all peripheral axons of corneal neurons lose the myelin sheath when they enter the corneal stroma. Fibers spread in a radial fashion parallel to the corneal surface.1

Our proposed study will explore the relationship of decreased corneal sensation, a potentially devastating eye condition secondary to CIDP. Decreased corneal sensation may lead to neurotrophic keratitis; which describes corneal diseases due to impairment or loss of corneal sensation leading to epithelial defects and corneal ulcers. This may be caused by many ocular and systemic diseases such as Diabetes or Stroke. Corneal innervation is important for the maintenance of corneal structure and function, and provides protective mechanisms against factors that might be potentially damaging to the cornea. Innervation also plays an important trophic function in corneal repair in relation to disease, trauma or surgery. Denervation and decreased corneal sensitivity are associated with impairment of epithelial and endothelial cell function, increased epithelial and endothelial permeability, decreased cell migration and cell mitosis. In addition, denervated corneas are predisposed to epithelial or stromal abnormalities, recurrent erosion, impaired wound healing and infection.2

Although corneal nerves lose their myelin sheath as they enter the stroma, the association of a demyelinating disease affecting these nerves cannot be excluded. This may be because trigeminal nerves can be affected at different levels (the nucleus in the pons, the Gasserian ganglion, the trigeminal ophthalmic branch, the nasociliary nerve, or the long ciliary nerve). Also, nerves without central myelin throughout their length can be affected in CIDP. For example, CNVIII has peculiar myelin as it has central myelin for the majority of its length, except for a short distal segment which has peripheral myelin.6 There is one case report correlating findings of hearing loss and vestibular dysfunction for over a 6-year period in patients with CIDP.

OUR STUDY