Non-invasive dural stimulation in mice: A novel preclinical model of migraine.

BACKGROUND: Migraine is characterized by a collection of neurological symptoms in the absence of injury or damage. However, several common preclinical migraine models require significant damage to the skull to stimulate the dura mater, the likely source of afferent signaling leading to head pain. The goal of this study was to determine whether dural stimulation can be performed in mice using an injection that does not cause injury or damage. METHODS: Using mice, injections of stimuli were administered to the dura mater through the soft tissue at the intersection between the lambdoidal and sagittal sutures. This technique did not require a permanent cannula nor did it cause damage to the skull or dura. Following injection of noxious stimuli, migraine-like behaviors were measured including cutaneous allodynia and facial grimace. The retrograde tracer fluorogold was applied onto the dura using the same injection technique to label trigeminal ganglion cell bodies, which were then testing in vitro using patch-clamp electrophysiology. RESULTS: Dural injection of allyl-isothiocyanate, low pH, interleukin-6, or inflammatory soup but not vehicles, led to cephalic/extracephalic allodynia. Facial grimace responses were also observed with allyl-isothiocyanate, pH 6.0, and interleukin-6. Stimulation with interleukin-6 causes priming to normally subthreshold pH 7.0 stimulation of the dura following resolution of the initial interleukin-6 behavior. Systemic injection of sumatriptan at the time of dural stimulation with inflammatory soup decreased the resulting cutaneous hypersensitivity. Trigeminal ganglion cell bodies retrogradely labeled from the dura had low pH-evoked currents similar to those generated by acid-sensing ion channels. CONCLUSION: Non-invasive dural stimulation in mice can be used as a model of migraine in the absence of injury.

The Outcomes of Extensor Tendon Repair Based on Timing of Repair.

Background: Little is known regarding the effect timing of repair has on extensor tendon repair results. The purpose of this study is to determine if a relationship exists between the time of extensor tendon injury to extensor tendon repair and patient outcomes. Methods: A retrospective chart review was conducted on all patients that underwent extensor tendon repair at our institution. The minimum time to final follow-up was 8 weeks. Patients were then divided into two cohorts for analysis; those that underwent repair less than 14 days after injury and those that underwent extensor tendon repair at or greater than 14 days after injury. These cohorts were further sub-grouped by zone of injury. Data analysis was then completed using a two-sample t-test assuming unequal variance and ANOVA for categorical data. Results: A total of 137 digits were included in final data analysis, with 110 digits repaired less than 14 days from injury and 27 digits in the greater than or equal to 14 days to surgery group. For zones 1-4 injuries, 38 digits were repaired in the acute surgery group and eight digits in the delayed surgery group. There was no significant difference in final total active motion (TAM) (142.3° vs. 137.4°). Final extension was also similar between the groups (2.37° vs. 2.13°). For zones 5-8 injuries, 73 digits were repaired acutely, and 13 digits were repaired in delayed fashion. There was no significant difference in final TAM (199.4° vs. 172.7°). Final extension was also similar between the groups (6.82° vs. 5.77°). Conclusions: We found time from extensor tendon injury to surgical repair did not affect final range of motion when comparing acute repair within 2 weeks from injury or delayed repair greater than 14 days from injury. Additionally, there was no difference in secondary outcomes, such as return to activity or surgical complications. Level of Evidence: Level IV (Therapeutic).

Extensor Tendon Repair Outcomes Based on Zone of Injury.

BACKGROUND: The purpose of this study was to examine the clinical outcomes of extensor tendon repairs based on zone of injury. METHODS: A retrospective chart review was conducted on all patients who underwent primary extensor tendon repair at our institution. Extensor tendon repairs were performed using a multiple figure-of-8 suture technique for extensor zones 1-4 and a modified Kessler suture technique for extensor zones 5-8. Inclusion criteria included a minimum of 8 weeks of follow-up, complete data available for review, and extensor tendon injury requiring primary surgical repair. RESULTS: A total of 132 digits were included for analysis: 46 digits in zones 1-4 and 86 digits in zones 5-8. The operative time for zone 1-4 injuries averaged 88.96 minutes, and the operative time for zone 5-8 injuries averaged 114.42 minutes. Final extension was found to be 2.33° for zones 1-4 and 6.66° for zones 5-8. Final flexion was found to be 141.4° for zones 1-4 and 195.3° for zones 5-8. There was 1 infection identified in zones 1-4 and 7 in zones 5-8. CONCLUSIONS: Surgically repaired extensor tendons in zones 1-4 were found to have a statistically significant worse final flexion compared with surgically repaired extensor tendons in zones 5-8. No significant differences were found in final extension, complication rates, and time to full activity. Operative times for zone 5-8 tendon repairs were found to be significantly longer than operative times for zone 1-4 repairs, possibly due to more complex injury patterns seen in the more proximal zones.