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Patients with hypertension appear to carry a higher risk for developing trigeminal neuralgia, a Taiwanese study showed.

Through about three years of follow-up, patients with high blood pressure were about 50% more likely to develop trigeminal neuralgia than those with normal BP (HR 1.51, 95% CI 1.19 to 1.90), Shin-Liang Pan, MD, PhD, of National Taiwan University in Taipei, and colleagues reported in the Oct. 25 issue of Neurology.

"Our findings therefore provide evidence for a temporal association between hypertension and trigeminal neuralgia," they wrote, adding that "further long-term follow-up study would be required to validate our findings and to investigate the underlying pathophysiologic mechanism."

Although the exact cause of trigeminal neuralgia is unknown, there is evidence to suggest that it could be caused by compression of the nerve by a tortuous vessel, which leads to demyelination, according to the researchers.

Cerebral vascular tortuosity has been associated with hypertension, they added.

Previous studies that have looked into a possible connection between hypertension and trigeminal neuralgia have yielded mixed results, so Pan and his colleagues wanted to explore the relationship using the National Health Insurance claims database in Taiwan, which covers nearly all residents of that country.

The analysis included 138,492 adults with at least two ambulatory visits with a principal diagnosis of hypertension compared with 276,984 randomly selected people without hypertension matched by age and sex. Those with trigeminal neuralgia at baseline were excluded.

At baseline, the mean age in both groups was 57, and about half of the individuals were female. Hyperlipidemia was more prevalent in the hypertension group (9.7% versus 7.4%, P<0.0001).

During a median follow-up of 31.8 months, trigeminal neuralgia developed in 121 patients in the hypertension group and 167 in the control group (0.09% versus 0.06%), a difference that remained significant after adjustment for demographics and medical comorbidities.

Pan and colleagues noted in their paper that the most plausible explanation for the relationship is that hypertension is inducing arterial tortuosity, which is compressing the trigeminal nerve and resulting in ectopic excitation and ephaptic transmission.

But an additional possibility is that both hypertension and trigeminal neuralgia share a common cause.

"Some studies have suggested that vascular compression of the ventrolateral medulla is associated with a subgroup of patients with essential hypertension," the researchers wrote. "It raises a possibility that the link between hypertension and trigeminal neuralgia seen in our study may be attributed to a common etiology, namely, neurovascular compression at the brainstem."

Various studies have failed to support that possibility, however.

The authors noted that the study was limited by the use of diagnostic codes to determine all diagnoses, the lack of some information regarding risk factors for hypertension, the follow-up time of only three years, and the uncertain generalizability to ethnic groups other than those of Chinese ancestry.

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