Faculty Bibliography

OBJECTIVES: (1) Present a unique case of partial necrosis of the dorsal tongue caused by an endotracheal tube; (2) highlight the importance of verifying proper endotracheal tube positioning during cases requiring prolonged intubation. METHODS: Case report and literature review. RESULTS: A 50 year-old man underwent total thyroidectomy and bilateral lymphadenectomies for papillary thyroid carcinoma. A nerve monitoring endotracheal tube was used during the case. Postoperatively, the patient reported tongue pain and examination revealed partial necrosis of his dorsal tongue. On follow up, the patient had improved tongue pain and well-healing dorsal tongue. DISCUSSION: We present the a case of tongue ischemia and partial necrosis due to oral endotracheal intubation, specifically with a nerve monitoring endotracheal tube, which has not previously been reported in the English literature. Tongue necrosis due to compression by an endotracheal tube during prolonged intubation is unusual, however surgeons, anesthesiologists and those involved in the care of intubated patients should consider the potential for this complication when orienting and securing endotracheal tubes. CONCLUSIONS: This unique case of tongue necrosis underscores the importance of proper endotracheal tube positioning during prolonged intubation

The endolymphatic hydrops seen in Menire's disease (MD) results from an inner ear fluid disequilibrium that has a suspected inherited component. Aquaporin-2 and aquaporin-4 (AQP2 and AQP4) water transport proteins may contribute to abnormal fluid homeostasis seen in MD. Our objective was to screen for sequence alterations in AQP2 and AQP4 genes in a northern European population with MD. Amplification for AQP2 (n = 18) and AQP4 (n = 30) was performed for patients with MD. Sequences were screened with denaturing high powered liquid chromatography (DHPLC) and confirmed with sequencing. Allele frequencies were compared with previously reported normal populations. We found that DHPLC failed to identify sequence alterations in any sample. Sequencing identified three intronic and one 3' untranslated region polymorphism in AQP2, and one polymorphism upstream from the start codon in AQP4. Two of the AQP2 intronic allele frequencies showed an A and C allele enrichment, respectively, compared with a reported mixed population (0.389 A vs. 0.00 A; 0.389 C vs. 0.00 C, p<0.001). The remaining polymorphism showed statistical difference from three non-Caucasian populations (0.611 A vs. 0.389 A, 0.375 A, and 0.280 A, p<0.05). The AQP4 allele frequency in the MD population was statistically different from a previously published Japanese population (0.800 G vs. 0.620 G, p = 0.0053) but not from a reported Caucasian population. We concluded that aquaporin polymorphisms may contribute to MD. Additional studies are needed to confirm these findings in well-defined population isolates and to determine if these polymorphisms lead to altered AQP protein function or levels

OBJECTIVES: To present a rare case of facial nerve paraganglioma and novel use of a processed allograft for facial nerve reconstruction. STUDY DESIGN: Case report and review of the literature. METHODS: A 34 year old female presented with progressive onset right sided facial palsy for 5 months. CT and MRI demonstrated an irregular mass in the right facial nerve canal from the intratympanic segment to the stylomastoid foramen. RESULTS: Following transmastoid resection, the defect was repaired using processed allograft. Pathologic analysis was consistent with a paraganglioma. Facial nerve paraganglioma is a rare entity that has been reported only 10 times in the literature. CONCLUSIONS: Traditional methods of facial nerve reconstruction, including autologous and cadaveric grafting, can lead to significant patient morbidity. Autologous nerve grafts are the 'gold standard' for superior regenerative capability, but are limited by the length and potential neuroma formation at the donor site. Allogenic grafts from donors or cadavers have shown some efficacy, but can require immunosuppression. The Avance nerve graft is a cadaveric graft, processed and decellularized to maintain an extracellular matrix with laminin and intact endoneural tubes, thus providing support for the growing axon without generating an immune response. Initial studies of the Avance graft in animals and humans have examined repair of peripheral nerves, but this is the first reported case of human facial nerve reconstruction

Spike-timing-dependent plasticity (STDP) has attracted considerable experimental and theoretical attention over the last decade. In the most basic formulation, STDP provides a fundamental unit - a spike pair - for quantifying the induction of long-term changes in synaptic strength. However, many factors, both pre- and postsynaptic, can affect synaptic transmission and integration, especially when multiple spikes are considered. Here we review the experimental evidence for multiple types of nonlinear temporal interactions in STDP, focusing on the contributions of individual spike pairs, overall spike rate, and precise spike timing for modification of cortical and hippocampal excitatory synapses. We discuss the underlying processes that determine the specific learning rules at different synapses, such as postsynaptic excitability and short-term depression. Finally, we describe the success of efforts toward building predictive, quantitative models of how complex and natural spike trains induce long-term synaptic modifications

While it has been appreciated for decades that synapse location in the dendritic tree has a powerful influence on signal processing in neurons, the role of dendritic synapse location on the induction of long-term synaptic plasticity has only recently been explored. Here, we review recent work revealing how learning rules for spike-timing-dependent plasticity (STDP) in cortical neurons vary with the spatial location of synaptic input. A common principle appears to be that proximal synapses show conventional STDP, whereas distal inputs undergo plasticity according to novel learning rules. One crucial factor determining location-dependent STDP is the backpropagating action potential, which tends to decrease in amplitude and increase in width as it propagates into the dendritic tree of cortical neurons. We discuss additional location-dependent mechanisms as well as the functional implications of heterogeneous learning rules at different dendritic locations for the organization of synaptic inputs