according to the international headache society ( ihs ) , classical trigeminal neuralgia ( tn ) is defined as  a unilateral disorder characterized by brief electric shock - like pains , abrupt in onset and termination , limited to the distribution of one or more divisions of the trigeminal nerve  .
this is different from symptomatic tn , which is defined by ihs as  pain indistinguishable from classical tn but caused by a demonstrable structural lesion other than vascular compression  .
patients often describe the pain as attacks or paroxysms , which may last for a few seconds to 2  min .
interestingly between paroxysms there is a refractory period in which the pain can not be triggered and the patient is asymptomatic .
the intensity of the pain is severe and the quality is usually described as electric shock - like , sharp , stabbing , or shooting .
the pain might be triggered spontaneously or by light touch in a specific area or simply by eating or talking .
tn is considered to be a rare disease with an annual incidence of 5.9/100,000 women and 3.4/100,000 men in the usa .
the incidence increases with age and tends to be higher in women at all ages with a male to female ratio of 2:3 .
the trigeminal nerve root entry zone has been found to be compressed by an aberrant loop of artery or vein , which ultimately leads to demyelination of the trigeminal nerve .
furthermore , it has been demonstrated that tn is more common in patients with multiple sclerosis and an elevated relative risk has been associated with hypertension ( htn ) , particularly among women .
it has been suggested that patients with tn have arterial tortuosity , which may lead to increased arterial pulse pressure waveforms secondary to vascular stiffness .
however , very few studies have explored the relationship between htn and tn [ 2 , 4 ] .
therefore , the objective of this study was to determine the prevalence of htn in patients diagnosed with classical tn and describe the characteristics of classical tn including age , gender and race among the patient population seen at the orofacial pain and oral medicine center at the usc school of dentistry ( usc ofp - om center ) in los angeles , california , usa between june 2003 and august 2007 .
a retrospective chart review was conducted from the electronic medical record database ( soapware , fayetteville , ar ) at usc ofp - om center of over 3,000 patient records from june 2003 to august 2007 .
the study was approved by the university of southern california university park institutional review board and ethics committee ( usc upirb # up-07 - 00416 ) and has therefore been performed in accordance with the ethical standards laid down in the 1964 declaration of helsinki .
we identified all patients who were diagnosed with tn using the chart searcher function implemented in the soapware program with the appropriate search terminology .
all patients were clinically diagnosed as having tn by the faculty , or residents under the supervision of faculty .
a thorough history and head and neck exam was performed for every patient along with necessary radiographic investigations to rule out all potential dental and bony pathologies .
brain mri with and without contrast was done for all patients prior to initiating treatment . only patients with classic tn ( idiopathic ) without any obvious pathology such as multiple sclerosis , plaques , tumors , and abnormalities of the skull base were considered in our study .
inclusion criteria for tn included a history and clinical presentation that satisfied the international headache society criteria for classical tn .
dental caries , periapical lesions , periodontal pockets with bone loss , cracked teeth , hyperocclusion , non - vital teeth and other bony pathologies were excluded with a thorough diagnostic workup . from this subset of tn patients , those currently taking anti - hypertensive medications for a minimum period of 6  months and with a diagnosis of htn ( established by the patient s physician ) were considered as having both tn and htn . for the control group we identified thrice the number of age- and gender - matched controls from the usc ofp - om center using the existing electronic medical record database ( soapware ) .
inclusion criteria were gender - matched and age - matched controls ( matched within a 2-year range ) who may or may not have a diagnosis of htn .
all control patients with htn were diagnosed by their physician and were on anti - hypertensive medication .
chi - square test with yates correction and fisher s exact test were performed to calculate the p value .
chi - square test with yates correction and fisher s exact test were performed to calculate the p value .
the study population comprised of a total of 84 tn patients ( 54 female ; 30 male ) and age- and gender - matched controls ( n  =  252 ; 162 female ; 90 male ) between the ages of 33 and 93  years ( mean 65.3  years ) .
the racial characteristics of our patient population were as follows : caucasian ( 102 ) ; hispanic ( 117 ) ; asian ( 33 ) ; black ( 38 ) ; american indian ( 3 ) ; others ( 19 ) and unknown ( 24 ) .
thirty - one patients with tn reported having htn and were taking anti - hypertensive medication , out of which 13 of these patients were males and 18 were females .
. the odds ratio of having htn in tn is 1.24 ( 95% confidence interval , 0.72 ) .
the difference in prevalence of htn in tn cases versus controls was not found to be statistically significant using chi - square test with yates correction ( p  =  0.50 ) and fisher s exact test ( p  =  0.42 ) .
hispanics had the highest prevalence of htn in both tn and controls followed by caucasians.fig . 
1prevalence of htn in cases versus controls ; x axis tn cases and controls ; y axis prevalence of htn prevalence of htn in cases versus controls ; x axis tn cases and controls ; y axis prevalence of htn
the risk factors that predispose an individual to develop tn include age and female gender .
although , arterial hypertension has been reported as a risk factor for developing tn based on the theory of increased arterial tortuosity and pulse pressure , little or no epidemiologic data exist to validate this concept .
arterial stiffness has been associated with the development of htn   and its association with tn has been investigated , but this relationship has not been established since studies failed to demonstrate that patients with tn have an increase in arterial stiffness . in a population - based study of tn patients conducted in rochester , minnesota , 25% (
19 out 75 ) of the patients with tn were found to have htn with an odds ratio of 1.96 ( 95% confidence interval , 1.23 ) . in our study , we have found the prevalence of htn in tn to be 37% compared to the 32% seen in the control population .
the reported rates of htn in the normal population have ranged from 28.7 to 29.3% [ 7 , 8 ] .
the slight increase in the prevalence of htn in the control group might be attributed to the fact that our sample is a convenience sample .
the 5% difference in the prevalence of htn between the two groups was not statistical significant .
this might also be due to our sample size , which was too small to show a statistically significant difference .
also , tn is a rare disease , with an overall prevalence of 0.10.2 per 1,000 and an incidence ranging from about 45/100,000/year , and therefore it is difficult to obtain a large tn patient sample . larger population - based studies might provide more evidence regarding the association between tn and htn . in our study
, htn was not found to be a significant risk factor in patients with tn .
the limitations of our study include the following : ( 1 ) retrospective chart review , ( 2 ) convenience sample , which will restrict the extrapolation of prevalence data to general population , and ( 3 ) lack of data regarding the duration of htn , which will be important as the vascular stiffness and nerve compression may worsen with prolonged hypertension . in general , retrospective studies are not the best way to study risk factors for diseases .
therefore , further prospective studies , with an accurate clinical assessment of htn , are needed to conclusively clarify the possible relationship between htn and tn . to the best of our knowledge ,
our data show that hispanics had the highest prevalence of tn followed by caucasians in comparison to other races .
since the los angeles area has a large population of hispanics this could explain the higher prevalence of tn noted in hispanics in this study .
however , our study is comprised of a sample size with a very diverse racial composition , which prevents the racial differences from this study from being extrapolated to the general population of the united states . in conclusion ,
our results suggest that there is no correlation between htn and the development of tn .
since , both tn and htn are seen in the elderly , it is possible that htn is simply a co - existing condition in patients with tn .
this conclusion should be taken with caution as this is a retrospective study and further prospective studies , with an accurate clinical assessment of hypertension , are needed to conclusively clarify the possible relationship between htn and tn .
 it is unclear whether hypertension ( htn ) is a predisposing factor for the development of trigeminal neuralgia ( tn ) . 
 the purpose of this study was to determine the prevalence of htn in tn patients and controls at the usc orofacial pain and oral medicine center . 
 a retrospective chart review was conducted from a database of over 3,000 patient records from 2003 to 2007 . 
 we identified patients diagnosed with tn with or without htn . 
 a total of 84 patients ( 54 females ; 30 males ) between the ages of 33 and 93  years were diagnosed with tn ; 37% had tn with htn and 32% of controls had htn . 
 the increased prevalence of htn in the tn patients was not statistically significant ( p  =  0.50 ) . since 
 , both tn and htn are seen in the elderly , it is likely that htn is simply a co - existing condition in patients with tn and not a risk factor for its development . 
Introduction
Materials and methods
Statistical analysis
Results
Discussion