Specificity and Sensitivity of Temporalis ES2 Measurements in the Diagnosis of Chronic Primary Headaches

We have evaluated the specificity and sensitivity of temporalis ES2 measurements for the diagnosis of primary headaches. Ninety-four outpatients diagnosed according to IHS criteria were prospectively included: 25 had chronic tension-type headache (code 2.2.), 15 episodic tension-type headache (code 2.1.), 20 migraine without aura (code 1.1.) and 34 chronic daily headaches with daily analgesics/ergotamine abuse (code 8.2.). In chronic tension-type, the sensitivity of the ES2 test was 84% at the 0.1 and the 0.5 Hz, but only 56% at the 2Hz stimulation rates. Its specificity was 100% at 0.1Hz, 90% at 0.5Hz and 95% at 2Hz compared to migraine; positive predictive values were at similar levels. Sensitivity of ES2 at 0.1 Hz was 67% in episodic tension-type headache, but its positive predictive value versus migraine was excellent. Comparing chronic tension-type headache and analgesic abusers, the specificity and positive predictive value of the ES2 test for diagnosing chronic tension-type headache were less satisfactory (60%) while the negative predictive values, however, remained good (83% at 0.1Hz).
The results confirm that the temporalis ES2 test has a higher diagnostic sensitivity in chronic and episodic tension-type headache, but that it has a high negative predictive value for both types of tension-type headache compared to other primary headaches. For diagnostic purposes, the 0.1Hz stimulation rate seems optimal. The 2Hz stimulation rate is the least sensitive, although it may induce total disappearance of ES2 in up to 40% of patients. ES2 is of limited usefulness for separating chronic tension-type headache and chronic drug-abuse headache, possibly because the latter group comprises both tension-type headache and migraine patients.