Abstract
Purpose::
To explore the use of anticonvulsant drugs to modulate corneal pain. Parallels exist between corneal pain and migraine headache as well as between corneal pain and neuropathic pain. In migraine, a cortical spreading depression activates the trigeminal nucleus caudalis. Craniovascular pain is transmitted through the ophthalmic division of the trigeminal nerve as it is in corneal pain. 2 large randomized placebo-controlled double-blinded clinical trials conducted in patients with 3-12 migraine headaches per month showed that 100 mgs of topiramate daily significantly reduced the average number of migraines. Topiramate blocks voltage-dependent sodium channels, potentiates gamma-aminobutyric acid mediated chloride currents and blocks kainiate receptors. Similarities between biochemical and pathophysiologic phenomena seen in some epilepsy and neuropathic pain models have raised the option of using anticonvulsants to treat neuropathic pain disorders. Given that topiramate is effective in the management of migraine and painful diabetic neuropathy, it was chosen for this study.
Methods::
NM is a 28 year-old female with post-traumatic recurrent corneal erosions treated with bandage contact lenses, Muro-128, doxycycline, stromal micropuncture, and LASEK over the course of 4 years. Because of persistent episodes of corneal pain, she was prescribed topiramate.
Results::
Prior to starting topiramate therapy, NM had experienced 3-4 awakenings due to pain at night and 5-6 episodes of spontaneous tearing and pain during the day. She started topiramate at 25 mg po qhs without significant change in her symptoms. After one week, the dose was escalated to 50 mg po qhs, and within one day, she experienced 0-1 awakenings at night. She had approximately 2-3 episodes of pain and tearing during the day. The dose was escalated to 100 mg po qhs. At that dose, the patient experienced pain relief but complained of nausea. The dose was changed to 50 mg po BID but the nausea persisted. The patient’s topiramate was weaned off to determine whether her symptom relief was due to the medication or due to improvement in her condition. Once off the topiramate, NM’s nausea resolved but her corneal symptoms returned at the same frequency as prior to the initiation of topiramate. Therefore, she was restarted on topiramate 50 mg po qhs with rapid onset of improvement in her symptoms and without nausea.
Conclusions::
Anticonvulsants such as topiramate may be effective in the management of pain due to recurrent corneal erosions. Further research will be necessary to better understand the pathophysiology behind corneal pain, but this initial foray appears promising.
Keywords: cornea: clinical science • trauma • pathobiology