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11 Cards in this Set
- Front
- Back
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What nerve and fiber type cross with a Martin-Gruber anastomosis? To what muscles?
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motor axons from the median nerve (typically the anterior interosseous) to the ulnar. Muscles innervated include the abductor digiti minimi, the FDI (most common), or the adductor pollicis or deep head of the FPB.
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What is the occurrence of a Martin-Gruber anastomosis in the normal population?
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15-30%.
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Describe the most common incidence when a MGA is suspected. What is the most important differential?
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When below elbow stim of the ADM is significantly less than at wrist stim (greater than 10% drop). Most important differential is conduction block of the ulnar nerve in the forearm.
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If there is an MGA at the ADM, what NCS should you do after the ulnar?
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Check the median at the wrist and antecubital fossa. The AC median CMAP amplitude recorded at the ADM should make up the difference seen on wrist to BE ulnar studies.
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Why is recording an MGA over the FDIM more difficult than at the ADM?
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Even though MGA to the FDIM is more common, it is harder to differentiate because of volume conduction of the thenar eminence to that area. The best way to identify it is to look for a relative increase in amplitude at the median antecubital fossa in comparison to the wrist.
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Describe the findings and diagnosis of a MGA to the deep FPB or adductor pollicis.
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Median antecubital will have a higher amplitude than wrist. Ulnar at wrist, recording over thenar eminence will have a higher amplitude than below elbow.
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What two characteristic findings are there with a MGA and CTS?
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Positive deflection with stim at the antecubital fossa and recording at the thenar eminence. Overly fast CV with stim at the AC fossa when compared to the wrist.
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Typically, what is the fastest CV of the median nerve?
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75 m/s.
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Where is the cubital tunnel?
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Underneath the aponeurosis of the flexor carpi ulnaris.
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Describe the course and innervation of the anomalous accessory peroneal nerve.
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Splits off the superficial peroneal nerve and travels along with it, though wraps laterally on the foot. Innervates the lateral aspect of the extensor digitorum brevis, which is usually wholly innervated by the deep peroneal nerve (the DPN still innervates the medial aspect).
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What is the typical NCS finding with an accessory peroneal nerve?
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decreased CMAP amplitude while recording over the EDB at the ankle when compared to the popliteal fossa and below the fibular neck. This is confirmed by stimulating just posterior to the lateral malleolus.
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