Cortical reintegration after facial allotransplantation.

Neural plasticity of the brain or its ability to reorganize following injury has likely coincided with the successful clinical correction of severe deformity by facial transplantation since 2005. In this study, we present the cortical reintegration outcomes following syngeneic hemifacial vascularized composite allograft (VCA) in a small animal model. Specifically, changes in the topographic organization and unit response properties of the rodent whisker-barrel somatosensory system were assessed following hemifacial VCA. Clear differences emerged in the barrel-cortex system when comparing naïve and hemiface transplanted animals. Neurons in the somatosensory cortex of transplanted rats had decreased sensitivity albeit increased directional sensitivity compared with naïve rats and evoked responses in transplanted animals were more temporally dispersed. In addition, receptive fields were often topographically mismatched with the indication that the mismatched topography reorganized within adjacent barrel (same row-arc bias following hemifacial transplant). These results suggest subcortical changes in the thalamus and/or brainstem play a role in hemifacial transplantation cortical plasticity and demonstrate the discrete and robust data that can be derived from this clinically relevant small animal VCA model for use in optimizing postsurgical outcomes.NEW & NOTEWORTHY Robust rodent hemifacial transplant model was used to record functional changes in somatosensory cortex after transplantation. Neurons in the somatosensory cortex of face transplant recipients had decreased sensitivity to stimulation of whiskers with increased directional sensitivity vs. naive rats. Transplant recipient cortical unit response was more dispersed in temporary vs. naive rats. Despite histological similarities to naive cortices, transplant recipient cortices had a mix of topographically appropriate and inappropriate whiskered at barrel cortex relationships.

Response properties of whisker-associated primary afferent neurons following infraorbital nerve transection with microsurgical repair in adult rats.

The rodent whisker/trigeminal system, characterized by high spatial and temporal resolution, provides an experimental model for developing new therapies for improving sensory functions of damaged peripheral nerves. Here, we use controlled whisker stimulation and single-unit recordings of trigeminal ganglion cells to examine in detail the nature and time course of functional recovery of mechanoreceptive afferents following nerve transection with microsurgical repair of the infraorbital nerve (ION) branch of the trigeminal nerve in adult rats. Response measures include rapid vs. slow adaptation, firing rate, interspike intervals, latency, and angular (directional) tuning. Whisker-evoked responses, readily observable by 3 wk post-transection, recover progressively for at least the next 5 wk. All cells in transected animals, as in control cases, responded to deflections of single whiskers only, but topography within the ganglion was clearly disrupted. The time course and extent of recovery of quantitative response measures were receptor dependent. Cells displaying slowly adapting (SA) properties recovered more quickly than rapidly adapting (RA) populations, and for some response measures-notably evoked firing rates-closely approached or attained control levels by 8 wk post-transection. Angular tuning of RA cells was slightly better than control units, whereas SA tuning did not differ from control values. Nerve conduction times and refractory periods, examined separately using electrical stimulation of the ION, were slower than normal in all transected animals and poorly reflected recovery of whisker-evoked response latencies and interspike intervals. Results underscore the need for multiple therapeutic strategies that target different aspects of functional restitution following peripheral nerve injury.

Pediatric facial fractures: occurrence of concussion and relation to fracture patterns.

BACKGROUND: Children and adolescents with injuries resulting in facial fractures are a population that is potentially at risk for suffering concomitant concussion. Concussion results in a variety of physical symptoms and often affects cognition, emotion, and sleep. These effects can have a significant impact on academics and social functioning. Early recognition of concussion and active management have been shown to improve outcomes. The goal of this study was to describe the occurrence of concussion in patients sustaining facial fractures and to determine whether certain fracture types are associated with concussion. METHODS: We performed a retrospective review of patients aged 0 to 18 years who were evaluated in the emergency department of the Children's Hospital of Pittsburgh from 2000 to 2005 with an International Classification of Diseases, Ninth Revision code indicative of facial fractures. Data included demographics, documentation of concussion, and facial fracture type. Patients with intracranial injury were excluded from the study. Univariate χ2 analysis and logistic regression were performed to determine characteristics associated with concussion. RESULTS: Facial fracture was diagnosed in 782 patients. Ninety-one patients had an intracranial injury and were excluded, leaving 691 patients for evaluation. The mean age was 11.1 (SD, 4.6) years. Males made up 69.6% of patients, and 80.6% of patients were white. Concussion was diagnosed in 31.7% of patients. Age, sex, and race were not associated with concussion. Univariate analysis demonstrated that skull and orbital fractures were associated with higher rates of concussion, whereas maxillary fractures showed a trend toward higher rates of concussion, and nasal and mandible fractures showed a trend toward lower rates of concussion. Logistic regression analysis demonstrated the odds of having a concussion were higher in those with skull fractures (odds ratio, 2.3; confidence interval, 1.5-3.7). CONCLUSIONS: Nearly one third of pediatric patients with facial fractures in this retrospective series were diagnosed with a concomitant concussion. Our data suggest that a higher index of suspicion for concussion should be maintained for patients with concomitant skull fractures and potentially orbital and maxillary fractures. Given the possibility of a worse outcome with delayed concussion diagnosis, patients with facial fractures may benefit from more active early concussion screening.

The incidence of C5 palsy after multilevel cervical decompression procedures: a review of 750 consecutive cases.

STUDY DESIGN: Retrospective review of 750 consecutive multilevel cervical spine decompression surgeries performed by a single spine surgeon. OBJECTIVE: To determine the incidence of C5 palsy in a large consecutive series of multilevel cervical spine decompression procedures. SUMMARY OF BACKGROUND DATA: Palsy of the C5 nerve is a well-known potential complication of cervical spine surgery with reported rates ranging from 0% to 30%. The etiology remains uncertain but has been attributed to iatrogenic injury during surgery, tethering from shifting of the spinal cord, spinal cord ischemia, and reperfusion injury of the spinal cord. METHODS: We included patients undergoing multilevel cervical corpectomy, corpectomy with posterior fusion, posterior laminectomy and fusion, and laminoplasty. Exclusion criteria included lack of follow-up data, spinal cord injury preventing preoperative or postoperative motor testing, or surgery not involving the C5 level. Incidence of C5 palsy was determined and compared to determine whether significant differences existed among the various procedures, patient age, sex, revision surgery, preoperative weakness, diabetes, smoking, number of levels decompressed, and history of previous upper extremity surgery. RESULTS: Of the 750 patients, 120 were eliminated on the basis of the exclusion criteria. The 630 patients included in the analysis consisted of 292 females and 338 males. The mean age was 58 years (range, 19-87). The incidence of C5 nerve palsy for the entire group was 42 of 630 (6.7%). The incidence was highest for the laminectomy and fusion group (9.5%), followed by the corpectomy with posterior fusion group (8.4%), the corpectomy group (5.1%), and finally the laminoplasty group (4.8%), although these differences did not reach statistical significance. There was a significantly higher incidence in males (8.6% vs. 4.5%, P = 0.05). CONCLUSION: Incidence of C5 nerve palsy after cervical spine decompression was 6.7%. This is consistent with previously published studies and represents the largest series of North American patients to date. There is no statistically significant difference in incidence of C5 palsy based on surgical procedure, although there was a trend toward higher rates with laminectomy and fusion.