Unusual Case of a Brachial Plexus Disorder Eddie Patton Jr. M.D, Cecile Phan M.D., Y. Harati M.D. Baylor College of Medicine Neuromuscular Diseases

History This is the case of a 44 y/o right handed man who suffered from a sudacute onset of a slowly progressive right arm weakness and atrophy, particularly of the biceps, beginning 4 months before his presentation to clinic. Three weeks before presentation he developed right leg pain and weakness No history of back pain or trauma No history of bowel or bladder dysfunction

History PMH: Noncontributory PSH: Sinus surgery SH: denies tobacco, ETOH, or illicit drugs, animal groomer who lives at home with his wife FH: No history of muscle or nerve disorders ROS: Positive for bi-frontal headaches beginning 2 wks before presentation and decreased sleep

History Physical exam pertinent positives Severe atrophy of right biceps 4/5 strength in right suprascapular, deltoid, brachioradialis, triceps, hand intrinsics, illiopsoas, quadriceps, hamstring, tibialis anterior, extensor hallicus longus 3/5 strength in right wrist extensors 1/5 strength in right biceps Reflexes +1 right brachioradialis and biceps, +3 bilateral patellar and ankle Babinski absent bilaterally Sensation mildly decreased to LT and PP right lateral leg

Exam

EMG/NCS 1.3(>2.0) NC Left Motor Nerves F-wave Distal Latency Proximal Latency Distal Amp Proximal AMP MCV Long Thoracic 3.7 2.4 Musculocutaneous 5.2 6.1 Common Peroneal 60 3.8 12.8 5.3 5.5 46.7 Tibial 8.8 (<6.6) 18.5 9.1 4.7 43.3 Right Motor Nerves F-Wave Distal Latency Proximal Latency Distal Amplitude Proximal Amplitude MCV Median 27.0 3.3 7.6 9.7 9.9 54.7 Ulnar 30.0 2.9 6.5 12.7 11.6 63.9 Long Thoracic 4.2 1.3(>2.0) Axillary 12.4 Musculocutaneous NC Common Perponeal 74.0 3.9 14.1 5.7 5.0 42.2 Tibial 67.0 8.1 18.5 10.4 40.4(>42)

EMG/NCS Left Sensory Nerves Distal Latency Proximal Latency Distal Amp Proximal Amp MCV Dorsal Sural abs Right Sensory Nerves Median II 2.9 3.8 20 22.0 51.3 Ulnar V 2.6 3.6 14.7 10.0 50.0 Lateral antebrachial 3.0 (<2.6) Sural 4.8(<4.0) 18.0 29.2 Dorsal Sural Abs

EMG Summary Neurogenic signs in 3 proximal muscles of the right upper extremity (Biceps C5-6, Infraspinatus C5-6, Triceps C6-8) and one distal muscle (Flexor Carpi Radialis C6-7). +1 low amplitude reinnervation units in Biceps Neurogenic signs in 1 distal muscle (Tibialis Anterior) Comments: “Findings of patchy denervation of the right brachial plexus, predominantly in the C5 and C7 distribution with a non-conductible right musculocutaneous nerve. Mild involvement of the right L4/5 and S1 muscles”

Differential Diagnosis ? HNPP Focal variant of CIDP Vascular (ischemic steal syndrome, thoracic outlet syndrome, subclavian or axillary aneurysm) Radiation induced plexopathy Traction or mechanical injury Neuralgia Amyotrophy ( Parsonage-Turner Syndrome) Neoplasm Primary (Schwannoma or nerve sheath tumor) Secondary ( Pancoast tumor)

Further work-up MRI brachial plexus

Radiology “Abnormal thickening of the right brachial plexus probably at the level of the superior trunk with enlargement also of the right C5-C6 nerve roots”

Further Work-up? Focal biopsy of right brachial plexus mass

Semi Thin: onion-bulbs Neuro-filament: axial view of axon staining positive for NF within onion-bulb

Differential Diagnosis ? Focal nerve enlargement Schwannoma Neurofibroma Solitary circumscribed neuroma Perineuronoma Dermal nerve sheath myxoma Hybrid benign peripheral nerve sheath tumor Focal CIDP

Epithelial Membrane Antigen stain

S100

EMA and S-100 protein stains “ EMA confirms the formation of concentric rings of positively staining spindle cells consistent with perineurial cells. Although S100 is positive in axons, it is a dominant component of nonlesional nerve” “Subsequent review of electron microscopy shows both Schwann cells and cells with discontinuous basal lamina and occasional pinocytosis surrounding centrally placed axons”

Perineurioma 1978- Lazarus and Trombetta coined term after case of a 45 y/o man with a calf tumor Clinically presents as progressive loss of motor function Sensory deficit and pain are uncommon True tumor consists of whorls and fascicles of spindle cells with ultrastructure of perineurial cells Incomplete basal lamina Poorly formed tight junctions Pinocytotic vesicles Gold Standard- + EMA stain and – S-100 Neoplastic perineurial cells express immunoreactive epithelial membrane antigen (EMA) Schwann cells immunoreactive to S-100 protein

Treatment of Nerve Sheath Tumors Observation Surgical removal Controversial