Peripheral Lesions of the Arm: Focus on the Hand

C8,T1 Medical nerve Oppenens Pollocis C7, C8 Posterior Interosseos (Radial): Abductor pollicus longus radial and BUT brevis is MEDIAL C8, T1 Ulnar nerve Adductor pollicus C7, C8 Posterior Interosseos (Radial): Abductor pollicus longus and brevis C8,T1 Anrterior Interosseois (medial) Flexor pollicus longus http://boneandspine.com/muscles-of-hand-and-wrist/

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Cortical Knob Syndrome – central lesion to consider when patient presents with hand weakness PIC: https://www.researchgate.net/profile/Sirio_Cocozza/publication/268704920/figure/fig3/AS:295330215153669@1447423618759/Fig-3-Pre-and-post-central-gyrus-ROIs-for-conventional-MRI-analysis-T2-weighted-axial.png

B. arm Representation in the cerebral cortex A 27yo woman, a waitress, presents with 2 weeks duration of numbness at the base of the thumb on the dorsum of the hand. On exam, normal cranial nerves, and normal muscle tone but with mild weakness of left brachioradialis and moderate weakness of the wrist and finger extension, although full power in the other arm muscle including elbow extension. Reflexes are normal, Sensory exam found a small area of sensory loss over the anatomical snuff box, Examination of the legs was normal. What is the single most likely site of the lesion? A. C7 Nerve root B. arm Representation in the cerebral cortex C. Radial nerve at the spinal groove D. Posterior Cord of the brachial plexus E. Posterior Inteosseos nerve Wrist drop – compression at the spinal groove weakness of radial nerves except arm extension because the motor branch of the triceps and anconeus split off at the mid shaft area. Posterior Brachial cutaneous nerve splits mid shaft so sensation lost would be forearm or hand Tricep reflex spared Lesion distal to spinal groove may spare brachioradialis and extensor carpir radialis muscle Needs triceps Not correct D E – brachio rad/extension of wrist is prox distal branch PIN

C. Carpal tunnel Syndrome D. Median neuropathy at the elbow A 62 yo old retired secretary presents to the clinic complaining of painful tingling sensation and numbness in her left thumb, index and middle finger that wakes her at night. On exam, motor power in the left arm, forearm and hand is normal. There is subtle loss of pinprick and light touch on the distal first to third digits (at finger tips). Biceps and brachioradialis deep tendon reflexes are normal. A tracing from her medial nerve sensory NCS is shown (medial nerve SNAP latency is 4.0m), motos NCS and EMG are normal. What is the most likely diagnosis A. C6 radiculopathy B. C7 radiculopathy C. Carpal tunnel Syndrome D. Median neuropathy at the elbow E. Brachial Plexopathy C. Sensation is spared in the thenar eminenct because of the palmar sensory branch that innervates the thenar eminence OUTSIDE tunne Thenar muscls from the recurrent branch may be affecting showing atrophy and denervation on EMG  weaknes of thumb ABD and opposition PROLONGUED distal medial nerve SNAP latency (normal is < 4) More advanced will have a conduction block

A. Radial neuropathy at the spinal groove B. C7 radiculopathy A 73 yr old man with poorly controlled diabetes presents with complaints of painless weakness of extension of fingers in left hand. On exam, forearm extension and wrist extension and abduction (wrist extension in the radial direction) are normal in strength but wrist extension and adduction (wrist extension in the ulnar direction) are weak. Forearm supination is weak, particulary when testing with forearm extended but there is no pain with active supination. Finger extension at the MCP joints is weak as if thumb abduction in the plan of the palms and thumb extension at the IP and MC joint. Sensory exam is normal. On NCS, the superficial sensory radial nerve is normal. Triceps reflex is normal. What is the most likely diagnosis? A. Radial neuropathy at the spinal groove B. C7 radiculopathy C. Posterior Interosseous nerve palsy D. Radial neuropathy at the elbow E. Supinator Syndrome C. PIN – PURE MOTOR No obvious WRIST drop – ext carpi radialis is spared Wrist ext in ulnar direction (ext carpi ulnaris) No C7 – tricep reflex intact Supinator syndrome – post post interossus nerve palsy from compression at that muslces