Complex regional pain syndrome - I following eye injury.

Sir,

Complex regional pain syndrome (CRPS) commonly affects limbs with sensory and motor disturbances.[1] CRPS in the orofacial region has not been clearly defined. The signs and symptoms of CRPS in the face occur after significant traumatic event, e.g., a penetrating lesion on facial skin, tooth extraction, or surgical trauma to the craniofacial region and never as trivial injury.[2]

A 25-year-old male was referred to pain clinic with complaints of deep seated pain with cutaneous swelling and discomfort over left eye. Past history included a trivial swipe injury in the same eye with the tail of a cow. The initial symptoms of redness and lacrimation subsided with local eye drops and there was complete resolution of initial injury. After two months, patient started having deep seated orbital pain associated with swelling off and on around the eye with mild burning sensation. Patient was taking Tab Diclofenac 100 mg twice daily for one week. On examination, the patient had persistent pain, moist skin over left eye lid and minimal resolving oedema over left eye lids. Rest of the examinations in the patient was inconclusive. A diagnosis of CRPS I was suspected and he was prescribed Aceclophenac 100 mg BD, along with incremental doses of Gabapentin reaching 300 mg thrice a day for four weeks as an initial management. His pain and edema improved in one week and was pain free in three weeks.

Incidence of CRPS I is more common than CRPS II and comprises 90% of all cases of CRPS with a varied annual incidence of 5.5 to 26.2 new cases of CRPS I per 100,000.[3] The pathophysiologic mechanism of CRPS is multi-factorial and poorly understood. It includes peripheral and central sensitization along with inflammatory changes, altered sympathetic function, changes in the somatosensory cortex, genetic and psycho physiologic interactions.[1] Intermittent or persistent pain is a dominant feature with patients typically describing pain as a burning sensation which occurs spontaneously or spreads beyond the site of injury.[4] Clinical features supporting the diagnosis of CRPS I in our patient are the following: history of trivial injury, persistent peribulbar pain with occasional burning character and cutaneous hyperalgesia even after healing of primary pathology, recurrent oedema of eye lids, non-detection of obvious cause for the pain, increased moisture of skin during episode of oedema, and finally a favorable response to gabapentin.

An inflammatory injury in trigeminal nerve area had been shown to sensitize afferent nociception pathway and also microglia in spinal nucleus caudalis (Sp5C) nucleus and astrocytes at the borders of spinal nucleus interpolaris (Sp5I) and Sp5C nuclei of trigeminal nerve.[5] Photophobia and reflexive blinking after eye injury could induce sensitization of corneal afferent nociceptive pathways in eye. Cornea also has mechanical and polymodal nociceptors that are stimulated by lid movements over dry eye. Nociceptive afferent in iris may also become another source of nociception in response to pupillary dilation.[6] Abnormal sympathetic nerve response has also been seen in CRPS at different stages of its progression.[7] Post ganglionic sympathetic fibers following the carotid plexus have been seen entering the orbit along with ophthalmic artery and first and second divisions of trigeminal nerve. While travelling anteriorly, these sympathetic nerves supply eyelid muscles, skin of forehead and by following ophthalmic artery also regulate blood flow to ocular and orbital regions.[8] The abnormal proliferation of afferent sympathetic nerves around spinal dorsal root ganglion is responsible for maintaining pain in chronic pain conditions in other regions of body.[9] Such proliferations, however, have not been seen in trigeminal ganglia.[5]

A reduction of sympathetic flow has been held responsible for oedema and warmth in early stages of CRPS in addition to other local factors.[7] Early intervention is essential in CRPS to prevent up regulation and expression of adrenergic receptors on nociceptive fibers.[7]

The primary aim of the therapy is to relieve pain, improve function and provide psychological support to the patients. Nonsteroidal anti-inflammatory drugs have been partially helpful in our patient, as it controlled the peripheral component of the pain due to inflammation. However, the persistent neuropathic pain of CRPS I markedly improved after Gabapentin and ruled out the necessity of further investigations and treatment modalities described for CRPS.

Early aggressive management of CRPS has been described to produce excellent results[10] and this was evident in our patient too. Delaying can be debilitating and disabling. A mechanism-based approach and better understanding of its pathophysiology may eventually lead the pathway to successful management.[11]