Takuo Kuboki

Concurrent cervical and craniofacial pain A review of empiric and basic science evidence

Because many patients present themselves for treatment with both craniofacial and craniocervical pain, 2 questions arise: (1) What are the sensory and motor consequences of dysfunction in either of these areas on the other? (2) Do craniofacial and craniocervical pain have a similar cause? These questions formed the impetus for this review article. The phenomenon of concurrent pain in craniofacial and cervical structures is considered, and clinical reports and opinions are presented regarding theories of cervical-to-craniofacial and craniofacial-to-cervical pain referral. Because pain referral between these 2 areas requires anatomic and functional connectivity between trigeminally and cervically innervated structures, basic neurophysiologic and neuroanatomic literature is reviewed. The published data clearly demonstrate neurophysiologic and structural convergence of cervical sensory and muscle afferent inputs onto trigeminal subnucleus caudalis nociceptive and non-nociceptive neurons. Moreover, changes in metabolic activity and blood flow in the brainstem and cervical dorsal horn of the spinal cord in both monkeys and cats have been demonstrated after electric stimulation of the V1-innervated superior sagittal sinus. In conclusion, the animal experimental data support the findings of human empiric and experimental studies, which suggest that strong connectivity exists between trigeminal and cervical motor and sensory responses.

Haemodynamic changes in human masseter and temporalis muscles induced by different levels of isometric contraction

This study evaluated the influence of low contraction forces on intramuscular haemodynamics in human masseter and temporalis using near-infrared tissue spectroscopy. This method allowed the intramuscular haemoglobin (Hb) to be assessed dynamically before, during and after a 5, 15, 25 and 100% maximum voluntary contraction (MVC). Twenty volunteers, 10 males and 10 females, without pain or dysfunction in the masticatory system were included in this study. Data were recorded for 30 s before, 30 s during and 5 min after the four sustained contraction tasks. The results showed that all four levels of voluntary contraction produced a clear haemodynamic response (during and after contraction) in both muscles. For analytical purposes, the maximum Hb achieved after 100% MVC was set equal to 1.00. In the masseter the mean peak Hb during the 5, 15, 25 and 100% MVC was 0.49, 0.92, 1.30 and 1.73 while after the contractions it was 0.50, 0.65, 0.78 and 1.00, respectively. In the temporalis the peak Hb during the contractions was 0.23, 0.36, 0.48 and 0.66 and after the contractions 0.32, 0.45, 0.56 and 1.00, respectively. Repeated-measures analysis of variance revealed a significant main effect for the different contraction levels both in the masseter (during contraction, p = 0.001; after contraction, p<0.001) and the temporalis (during contraction, p = 0.002; after contraction, p<0.001). These data suggest that low levels of contraction induce a clear haemodynamic response, even at 5% effort. When compared, the masseter and anterior temporalis showed clearly different patterns for the Hb signal during the contraction (p<0.001) as well as after it (p = 0.007). Specifically, the Hb during the contractions in the masseter appeared more stable than in the temporalis, which showed a strong return to baseline. Obviously the contracting masseter had a stronger and more sustained venous occlusion than the contracting temporalis. It is speculated that variation in architecture between the two muscles contributes to these differences in blood flow.