Nerve Conduction Studies of the Larynx: Porcine Model and Human Application.

OBJECTIVE: There is a paucity of information in the literature about how electromyography (EMG) with nerve conduction studies (NCS) can be utilized in the field of neurolaryngology. The goal of this study was two-part: (1) to identify the NCS test parameters that best reflect underlying neurolaryngeal pathophysiology in a porcine model, and (2) to determine if comparable NCS parameters can be used to assess clinical laryngeal denervation injuries in patients. METHODS: Yukatan minipigs underwent general anesthesia with EMG and recurrent laryngeal NCS assessment. Recurrent laryngeal nerve (RLN) transection injury and uninjured RLN cases were included to determine NCS neuropathologic and normative findings, respectively. Our porcine analytic model was then applied to a clinical scenario of seven patients with RLN injury. RESULTS: The porcine model was able to differentiate and characterize normative and neuropathologic NCS changes. Clinical outcomes suggest that RLN NCS can be performed clinically and is overall well tolerated by in patients. Findings may serve as a useful tool to differentiate normal nerve function, neuropraxia, axonotmesis, and irreversible RLN injuries. CONCLUSION: This novel study is the first to demonstrate the feasibility and applicability of EMG with NCS in the evaluation of vocal fold function in a porcine model in addition to the clinical setting. Further studies are needed to better understand the clinical utility and predictive value in recovery of vocal fold paralysis.

Nerve Conduction Studies: Basic Concepts and Patterns of Abnormalities.

Nerve conduction studies are a key component of the electrophysiologic evaluation of the peripheral nerve system, and provide important information about the integrity of the large, myelinated axons, neuromuscular junctions, and muscle. Nerve conduction studies involve eliciting nerve action potentials at sites along a peripheral nerve and recording the response from another site along the nerve or from a muscle innervated by that nerve. Attention to details of test performance, use of well-established normative values, and knowledge of the patterns of abnormality produced by disorders that affect neuronal, axonal, and myelin sheath function are fundamental for proper interpretation of results.

Disturbances of visual motion perception in bipolar disorder.

OBJECTIVES: While cognitive deficits have been well documented in patients with bipolar disorder, visual perception has been less well characterized. Such deficits appear in schizophrenia, which shares genetic risk factors with bipolar disorder, and may contribute to disturbances in visual cognition and learning. METHODS: The present study investigated visual perception in bipolar disorder using psychophysical tests of contrast sensitivity, dot motion discrimination, and form discrimination. The relationship of these measures to mood state, medication status, and cognitive function was investigated. Sixty-one patients with type I bipolar disorder and 67 comparison subjects were tested. RESULTS: Results indicated a deficit in dot motion trajectory discrimination in both euthymic and ill individuals with bipolar disorder, as well as a global deficit in moving grating contrast sensitivity. Ill individuals with bipolar disorder were impaired in psychomotor processing, but this finding was not related to visual processing performance. CONCLUSIONS: These findings could be due to disturbances in specific visual pathways involved in the processing of motion properties, or to a more general deficit which impairs processing of temporally modulated stimuli.