1. 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

2. 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

3. 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

4. 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

5. Exam

6. 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)

7. 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

8. 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”

9. 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)

10. Further work-up
MRI brachial plexus

11. 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”

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

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

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

15. Epithelial Membrane Antigen stain

16. S100

17. 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”

18. 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

19. Treatment of Nerve Sheath Tumors
Observation
Surgical removal
Controversial