1. A 17 year old male with tremors and wasting of both hands
Teaching NeuroImages
Neurology
Resident and Fellow Section
© 2015 American Academy of Neurology

2. Vignette
A 17 years old male developed bilateral hand “tremulousness”, weakness and decreased muscle bulk over 6 months.
Bilateral extremity wasting with sparing of brachioradialis muscles (Figure 1) was evident.
With arms outstretched, distal mini-polymyoclonus (Video) occured.
Neurophysiology suggests a pure motor neuropathy (chronic denervative changes in C7-T1 roots).
MR spine (dynamic flexion sequences)1 (Figure 2) revealed cervical cord atrophy, dural sac anterior shifting and contrast-enhancing epidural compartment.
Ong et al.
© 2015 American Academy of Neurology

3. Imaging A C
Figure 1. Bilateral distal forearm wasting, sparing the brachioradialis muscles (A) (bold arrows). First dorsal interrosei (B),
hypothenar and thenar eminence atrophy (C).
Ong et al.
© 2015 American Academy of Neurology

4. Imaging * * * Ong et al. A B D A B C E
Figure 2. (A) Non-flexion T1W MR showing C7-T1 cord atrophy (arrowheads). (B and C) Flexion T2W MR shows anterior
shifting of the dural sac with flattening of cervical cord. Engorgement of epidural venous plexus (asterix)
which (D and E) enhanced with contrast (T1W ) (arrows). B C E *
Ong et al.
© 2015 American Academy of Neurology

5. Imaging
Video. Small amplitude, repetitive arrhythmic movements which were abrupt and shock-like, identifying mini-polymyoclonus, were seen in individual fingers when the hands were outstretched.
Ong et al.
© 2015 American Academy of Neurology

6. A case of Hirayama disease presenting with polymyoclonus
The constellation of features described suggest Hirayama disease2, postulated to be secondary to chronic segmental cord ischemia from repeated neck flexion over a tight dural sac.
The small amplitude, repetitive arrhythmic movements which were abrupt and shock-like characterizing mini- polymyoclonus, should not be mistaken for tremors.
REFERENCES
1. Chen CJ, Chen CM, Wu CL, et al. Hirayama disease: MR diagnosis. AJNR Am J Neuroradiol 1998; 19:365-8.
2. Hirayama K, Toyokura Y, Tsubaki T. Juvenile muscular atrophy of unilateral upper extremity: a new clinical entity. Psychiatr Neurol Jpn 1959; 61:
Ong et al.
© 2015 American Academy of Neurology