Bilaterally symmetric form of
• Sunil Pradhan et al
• Institute of human behavior and allied
sciences, New delhi.
• Neurology,vol.72,number 24,june16,2009.
• Hirayama disease (benign juvenile brachial spinal muscular
atrophy, benign juvenile muscular atrophy of distal upper
extremity, monomelic amyotrophy).
• Pure motor focal amyotrophy in distribution of c7,8,T1 spinal
• Sporadic, Men, second and early third decade.
• Muscular weakness and wasting of hand and forearm
• Oblique amyotrophy.
• Insidious onset, steadily progressive for 1-3 yrs..stable stage.
• Dynamic cord compression during neck flexion.
• Juvenile asymmetric segmental spinal muscular
• Describe bilaterally symmetric form of hirayama disease.
Materials and methods
• 106 (m-103,f-3)
• 14-32 yrs
• Two academic centers
• Patients registry
• 11 patients with symmetic form
• Clinical, edx, mri evaluation normal and neck flexion.
• Onset in teen and early 20s.
• Symmetric /asymmetric muscle atrophy in c7,c8,t1
• No sensory symptoms/signs
• Relative sparing of brachioradialis
• Tremulousness of fingers in outstretched hands
• Cold paresis
• Unilaterality ….replaced by MRI findigs
• Flattening of spinal cord against c5-6 vertebral bodies
• Forward movement of posterior cervical duramater,
• reduction in size of posterior cervical subarachnoid
• Contrast enhancing crescent shaped posterior cervical
s lateralis,tibialis anterior.
• Denervation potentials( positive sharp waves and
otentials)during rest state were compared in same
muscle in two sides.
• Reinervation potentials (large,wide polyphasic
potentials)studied in mild contraction in each muscle(3
• 10 sweeps of 100 msec duration-frozen –percent of
polyphasic potentials to number of MUP and compared.
• CMAP of median,ulnar,radial nerve were used to
document symmetry of disease.
• < 20% difference in CMAP of APB,ADM,EDC taken as
• SNC to rule out axonal forms of polyneuropathy
• All findings were compared with existing knowledge of
• 11/106 symmetrical
• All male
• Age 18-24(20.27)
• Started at mean 17.8 yrs progresed for 1-3 yrs (9),3-4
• 9 immunised for polio, none had h/o polio.
• 6 had onset in winter months
• None had preceding febrile illness
• All had weakness and wasting in c5,6 t1 myotomes
• 6 had partial brachioradialis wasting s/o c6 myotome
• Unilateral onset in 9 patients (R 6, L 3),bilateral in two.
• Autonomic dysfunction in all, (excessive sweating in
7,cold hands in 8,hair loss in 5)
• All had fasciculation at rest ,mini polymyoclonus in
• 7 had brisk DTR in lower limbs
• Neutral position-Symmetric cord atrophy in 9, T2 hyper
intensity in anterior lateral aspect of lower cervical spinal
cord in 7.
• Neck flexion-band like cord flattening in all (symmetric in
7,asymmetric in 4)crescent shaped enhancing epidural
• All had N SNAPs
• All had n emg in lower limbs
• All clinicallly symmetric form had < 20% difference in
• Quantitative asessment of percentage of acute
denervation and chronic renervation potentials showed
nearly symmetric involvement between right and left
• In this series of 106 patients nearly 10% showed
symmetric involvement of both upperlimbs.
• VS a form of ALS ‘brachial amyotrophic diplegia’ ‘flail
arm syndrome’ ‘man in barrel syndrome’-older age,
predominant c5-6 involvement, overt fasciculations,
gradual appearance of UMN or bulbar signs,avg survival
of 5 yrs,no dynamic MRI changes with neck flexion.
• Vs postpolio atrophy-no h/o polio,symmetrical and MRI.
• Short length of cervical dural canal that cannot
compensate for flexion related increased length of
vertebral canal. dural canal becomes tight during neck
flexion-anterior displacement of posterior dural wall and
spinal cord, spinal cord gets flattened against c5-6
vertebral body,cresent shaped posterior epidural space
with prominent venous plexus.
• Neck flexion related anatomic changes cause
mechanical and hemodynamic stress on anterior horn
cells in c7,8,T1
• Severe form of hirayama disease