hemicrania continua ( hc ) is an uncommon primary headache disorder characterized by a continuous , mild to moderate intensity , unilateral headache [ 14 ] .
most patients will experience superimposed exacerbations of more severe pain , often associated with ipsilateral autonomic symptoms .
headache for greater than 3  months fulfilling the following criteria : all of the following : unilateral pain without side shift , daily and continuous , without pain - free periods , moderate intensity , but with exacerbations of severe pain.at least one of the following autonomic features occurs during exacerbations and ipsilateral to the side of pain : conjunctival injection and/or lacrimation , nasal congestion and/or rhinorrhea , ptosis and/or miosis.a complete response to therapeutic doses of indomethacin.finally , not attributed to another disorder .
unilateral pain without side shift , daily and continuous , without pain - free periods , moderate intensity , but with exacerbations of severe pain .
at least one of the following autonomic features occurs during exacerbations and ipsilateral to the side of pain : conjunctival injection and/or lacrimation , nasal congestion and/or rhinorrhea , ptosis and/or miosis .
a complete response to therapeutic doses of indomethacin . finally , not attributed to another disorder .
there is a group of patients that meets the above criteria for hc , but has to discontinue indomethacin secondary to adverse effects , primarily involving the gastrointestinal ( gi ) tract .
the side effects can range from gastritis to severe bleeding , patients may also develop an allergy to indomethacin , see an elevation of blood pressure , or an exacerbation of asthma symptoms .
gabapentin is often used in an off label fashion for the treatment of neuropathic pain and is well tolerated from a side effect profile .
marinano da silva , alcantara , bordini , and speciali reported a case of a unilateral headache similar to hc that was responsive to gabapentin .
institutional review board approval was obtained for the study . a retrospective chart review of nine patients with hc between october 2006 and february 1 , 2008 .
inclusion criteria included men and women age 18 or above presenting to the headache center with a headache that meets ihs criteria for hc , including a response to indomethacin , but were unable to continue on indomethacin secondary to adverse side effects .
exclusion criteria included anyone under the age of 18 and anyone not meeting ihs criteria for hc including an adequate trial at therapeutic doses of indomethacin and response to indomethacin .
patients with concomitant disease , specifically involving pain were not excluded , although every effort was made to enroll patients where hc was their primary complaint .
this was decided since the purpose of this study was to examine gabapentin as an alternative therapy , indomethacin remains the gold standard .
points of measurement included the duration of disease which is considered to be from onset to completion of the study , temporal profile , duration of therapy , range of dose , and concurrent use of other medications for pain , concomitant disease , especially related to pain , reduction of pain , and the side effects of gabapentin .
the duration of therapy on gabapentin ranged from 3  months to 13  months with eight out of nine patients remaining on gabapentin at the end of the study .
one patient discontinued after reaching 3,600  mg a day due to lack of efficacy .
the other doses ranged from 600  mg to 3,600  mg per day of gabapentin .
one patient also on fentanyl patch 50  mcg every 72  h reported an 80% reduction in pain after reaching 2,400  mg of gabapentin .
the second patient was taking topiramate and became pain free upon reaching 600  mg of gabapentin.table  1treatment of hc with gabapentinpgardi / day ( mg)arirdg dose / day ( mg)rpdd ( months)tpdt ( months)cdcmse#1f41150gastritis1,5008/100/1013c5nonenonenone#2f5575gastritis2,4006/101/106c4lumbar radiculopathyfentanyl patch 50  mcg/72  hsedation#3f44300g.i . bleed 2 episodes3,6009/109/1025c6nonenonecognitive impairment#4f25150fatique9004/101/1036c12nonenonenone#5f46150gastritis9005/104/107c4nonenonenone#6f33150gastritis1,8008/100/1034c7nonenonevertigo#7m6375rectal bleed3,60010/104/1017c13nonenonenone#8f45300excerbation of asthma60010/100/108c5migrainetopiramate 50  mg / daynone#9f42250gastritis9005/100/103ep3atypical facial painnoneweight gainp patient , g gender , f female , m male , a age , rdi responsive dose of indomethacin , ari adverse reaction to indomethacin , rdg responsive dose of gabapentin , rp reduction of pain , dd disease duration , tp temporal profile , c chronic , ep episodic , dt duration of treatment , cd concomitant disease , cm concomitant medication , se side effects on gabapentin treatment of hc with gabapentin p patient , g gender , f female , m male , a age , rdi responsive dose of indomethacin , ari adverse reaction to indomethacin , rdg responsive dose of gabapentin , rp reduction of pain , dd disease duration , tp temporal profile , c chronic , ep episodic , dt duration of treatment , cd concomitant disease , cm concomitant medication , se side effects on gabapentin the seven patients that achieved the primary end point and reported a 5080% reduction of pain had doses ranging from 900 to 3,600  mg per day .
the one man reported a 50% reduction of pain and reached the maximum dose of 3,600  mg of gabapentin per day .
four patients achieved the secondary end point and reported being completely pain free on gabapentin .
the dose ranges for these patients were , 600  mg , 900  mg , 1,500  mg , and 1,800  mg / day respectively .
it should be noted that one of the four patients was also taking topiramate , which has been reported to be efficacious for hc [ 7 , 8 ] .
the patient , who reported no benefit , responded to indomethacin on two separate occasions but developed gi bleeding as a result of indomethacin .
the major side effects reported on gabapentin include sedation , cognitive impairment , depression , and weight gain .
none of the patients chose to discontinue gabapentin as a result of the above side effects .
hc was first described in 1981 and officially named by sjaastad and spierings in 1984 [ 9 , 10 ] .
hc was originally believed to be a rare primary headache disorder but more recent evidence suggests that hc is not rare , just under recognized . in the clinical setting , hc is characterized by a unilateral headache that is continuous and of mild to moderate severity .
the pain is usually reported as dull , aching , or pressure - like pain without associated symptoms .
exacerbations or more severe pain , lasting anywhere from 20  min to several days , are experienced in the majority of those with hc , and when present are associated with one or more autonomic symptoms on the ipsilateral side .
migrainous features , such as photophobia , phonophobia , nausea , and vomiting commonly occur during exacerbations of pain .
many patients will experience a sensation of a foreign body in their eye similar to sand or an eyelash on the affected side .
the pathophysiology of hc is not known , some scientist believe it is a subtype of migraine , while others believe it is more closely related to the trigeminal autonomic cephalalgias ( tac ) .
it was hoped that functional brain imaging would help to clarify our understanding of hc , but it revealed that hc is a distinct headache syndrome , not belonging to the migraine or tac group .
the scans revealed activation of the contralateral posterior hypothalamus and ipsilateral dorsal rostral pons , as well as activation of the ipsilateral ventrolateral midbrain , extending over the red nucleus and substania nigra and the bilateral pontomedullary junction .
these areas have been previously demonstrated to be the sites of activation in the tacs and migraine , ipsilateral activation hypothalamic activation in short - lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing ( sunct ) and cluster ; in hc the findings are reversed .
hc was not included in the first edition of the ichd - i , but is included within the other primary headaches section of the second edition of the ichd - ii .
hemicrania continua presents as two temporal profiles : an episodic form with distinct headache phases separated by periods of pain - free remissions , and a chronic form in which the headache persists without remission for years .
hc is chronic from onset in 53% of patients ; the disorder began in the episodic form and evolved into the chronic form in 35% , and it begins and remains episodic in 12% of patients .
this can occur by focusing exclusively on the ipsilateral autonomic features that accompany the painful exacerbations of hc .
similarly , focusing on the associated photophobia , phonophobia , nausea , and vomiting that may occur during exacerbations of hc may lead to misdiagnosing hc as migraine .
autonomic features on the ipsilateral side , which are present during exacerbations of hc , are at times also present during acute attacks of migraine .
hc is also distinguished from cluster headache and migraine by the presence of a continuous baseline headache that is usually unilateral and mild to moderate in severity .
the associated features of photophobia , phonophobia , nausea , and vomiting , as well as the ipsilateral autonomic features of cluster are absent with the continuous baseline pain of hc .
some patients are unable to tolerate indomethacin due to gi distress , renal disease , or concurrent anticoagulation therapy , and alternative types of therapy must be considered .
peres and silberstein demonstrated in a study using cyclooxygenase-2 inhibitors ( cox-2 ) , efficacy of celecoxib and rofecoxib , the latter of which has since been removed from the market .
they found 60% of patients who received celecoxib and 33% who received rofecoxib experienced a complete response .
there is one case in the literature of a unilateral headache similar to hc that did not respond to indomethacin , and many other standard headache agents , but was responsive to gabapentin at 1,200  mg per day .
there have also been two separate reports of melatonin being efficacious for hc , one case reported by spears , and three cases by rozen .
there have also been four cases in the literature of patients responding to topiramate , one by camarda et al .
, one by matharu et al . , and two cases by brighina et al . .
gabapentin is an antiepileptic drug that is approved for use in the adjunctive treatment of partial seizures with and without secondary generalization in patients over 12  years of age .
gabapentin is also indicated as adjunctive therapy in the treatment of partial seizures in pediatric patients age 312  years of age .
benefit has been reported in gabapentin treatment for hypobaric hypoxia - induced headache , high altitude headache , nummular headache , sunct syndrome , chronic cluster headache , post - dural puncture headache , and primary thunderclap headache just to mention headaches disorders [ 1826 ] .
the mechanism by which gabapentin exerts its analgesic action is unknown , but in animal models of analgesia , gabapentin prevents allodynia ( pain related behavior in response to a normally innocuous stimulus ) and hyperalgesia ( exaggerated response to painful stimuli ) .
the mechanism by which gabapentin exerts its anticonvulsant action is unknown , but in animal test systems designed to detect anticonvulsant activity , gabapentin prevents seizures .
gabapentin is structurally related to the neurotransmitter gamma - aminobutyric acid ( gaba ) but does not modify gaba a or gaba b radioligand binding , it is not converted metabolically into gaba or a gaba agonist , and it is not an inhibitor of gaba uptake or degradation .
gabapentin was tested in radioligand binding assays and did not exhibit affinity for a number of other common receptor sites including benzodiazepine , glutamate , n - methyl - d - aspartate ( nmda ) , quisqualate , kainate , strychnin - insensitive glycine , alpha 1 , alpha 2 , or beta adrenergic , adenosine a1 or a2 , cholinergic muscarinic or nicotinic , dopamine d1 or d2 , histamine h1 , serotonin s1 or s2 , opiate mu , delta or kappa , cannabinoid 1 , voltage sensitive calcium channel sites labeled with nitrendipine or diltiazem , or at voltage sensitive sodium channel sites labeled with batrachotoxinin a 20 alpha benzoate .
one patient reported an 80% reduction of pain on 2,400  mg of gabapentin but was also on the fentanyl patch .
there have been reports in the literature of enhancement of pain control on the combination of opioids and gabapentin [ 28 , 29 ] .
this patient met the primary endpoint , but the concomitant use of an opioid is a confounding factor .
this study demonstrates that gabapentin is a good choice for alternative therapy in the treatment of hc .
seven out of nine patients demonstrated at least a 50% reduction of pain on gabapentin , four patients becoming completely pain free .
the results of the study are confounded in two patients that were taking concomitant medications specifically fentanyl patch and topiramate .
another potential confounding factor is that a proton pump inhibitor was not initiated when patients had difficulty tolerating indomethacin .
clinically it may be prudent to first try initiating therapy with a proton pump inhibitor while continuing indomethacin prior to changing to gabapentin .
hc is a particularly difficult headache disorder to treat if the patient is not able to tolerate indomethacin , therefore alternative therapies are being sought to provide relief to this patient population .
the results of this study should be validated in a double - blinded randomized control trial .
 the objective of this study is to examine the efficacy of gabapentin for the treatment of hemicrania continua ( hc ) in cases where patients had difficulty tolerating indomethacin due to adverse effects . a retrospective chart review of nine patients with hc between october 2006 and february 2008 . 
 inclusion criteria included men and women age 18 or above presenting to the headache center with a headache that meets international headache society criteria for hc including a response to indomethacin , but were not able to continue on indomethacin secondary to adverse effects . 
 four patients report being pain free , three patients report a 5080% reduction of pain , one patient reports a 10% reduction of pain , and one patient reports no change in pain . 
 seven out of nine patients demonstrated at least a 50% reduction of pain on gabapentin , four patients becoming completely pain free . 
Introduction
Methods
Results
Discussion
Conclusions