Corneal Neurotization in the Setting of Facial Paralysis: A Comprehensive Review of Surgical Techniques

Abstract

Neurotrophic keratopathy is characterized by decreased corneal sensitivity, decreased reflex tearing, and poor corneal healing resulting in corneal injury. Without proper sensory innervation, the cornea undergoes continuous epithelial injury, ulceration, infection and eventually results in vision loss. In situations where patients have concomitant facial paralysis, such as after resection of a large vestibular schwannoma, the ocular health is further impaired by paralytic lagophthalmos with decreased eye closure and blink reflex, decreased tearing, and potential lower eyelid malposition. In patients with a dual nerve injury, the ocular surface is in significant danger, as there is increased environmental exposure in conjunction with the inability to sense damage when it occurs. Immediate recognition and care of the eye are critical for maintaining ocular health and preventing irreversible vision loss. The first modern corneal neurotization procedure was described in 2009. The ultimate goal in corneal neurotization is to establish subbasal plexus regeneration via transferring a healthy nerve to the corneo-limbal region. Corneal neurotization can be achieved either via a direct transfer of healthy nerve (direct approach) or via nerve graft interpositions (indirect approach). This is an emerging concept in the treatment of neurotrophic/exposure keratitis and over the past decade multiple direct and indirect approaches have been described in the attempt to restore corneal sensation and to prevent the devastating outcomes of neurotrophic keratitis. Knowledge of these techniques, their advantages, and disadvantages is required for proper management of patients suffering from neurotrophic keratitis in the setting of facial paralysis.

Characteristics of the ocular surface in neurotrophic keratitis induced by trigeminal nerve injury following neurosurgery

“…It is vital to thoroughly understand the mechanisms of the blink reflex when discussing trigeminal nerve damage combined with facial nerve damage. The corneal blink reflex is a loop between the facial nerve and the ophthalmic branch of the trigeminal nerve [ 12 ]. Previous studies found that decreased corneal sensitivity and decreased sub-basal nerve length were observed in all NK eyes [ 13 , 14 ].…”

A Prospective Study of Paul Tessier’s Technique in Paralytic Lagophthalmos Management

“…The course of recovery after using this technique showed no side effects, while in the gold weight other side effects were found such as extrusion, infection, visibility, distortion of the upper eyelid, Plastic, Reconstructive Surgery and Burn occasional astigmatism and the cost of the gold plate). 3,5,8 The aesthetic appearance of the upper eyelid and patients' satisfaction after Paul Tessier's technique of (LPS) muscle lengthening was found far higher than in patients after using gold weight technique reported in the literature. 10 Guillou-Jamard et al 4 published a study of 29 patients who were treated with (LPS) muscle lengthening by aponeurosis interposition as Paul Tessier's description.…”

“…Multiple ocular disorders like conjunctivitis, keratitis, corneal ulceration, and vision loss result from the lack of ocular protection. [1][2][3][4][5][6][7][8][9][10][11] Facial palsy treatment necessitates a multidisciplinary approach. If a spontaneous recovery is predicted, temporary procedures like as artificial tears, lid taping overnight, viscous ointments, temporary tarsorrhaphy and external weights of the eyelid are recommended.…”

“…A permanent surgical option, such as permanent tarsorrhaphy, palpebral springs, levator muscle lengthening, upper lid weights, or dynamic techniques, such as temporalis muscle transfer or cross-facial nerve grafting, is indicated if recovery is being missed or incomplete. [2][3][4][5][6][7][8] Paul Tessier described lagophthalmos as a lack of antagonistic relationship between the orbicularis oculi muscle and the upper eyelid levator in 1969. The (LPS) muscle is innervated by the common oculomotor nerve (III), not the facial nerve; hence it continues to function even if the facial nerve is injured.…”

Corneal Neurotization—Indications, Surgical Techniques and Outcomes

“…Corneal neurotization can be performed either by directly transferring a nerve from its original position to supply the cornea (direct corneal neurotization, DCN) or by connecting a nerve to the cornea via nerve graft conduit (indirect corneal neurotization, ICN) [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. Direct neurotization could perhaps achieve a faster clinical response, while indirect neurotization requires new axons to grow down the length of the nerve graft to the cornea and can take approximately 6 months.…”