Thursday, May 7, 2009

Cervical spondylotic amyotrophy (CSA)

Shinomiya K reported dissociated motor loss due to cervical spondylosis and disc herniation presenting with deltoid paresis in the absence of sensory deficits or myelopathy (5). The clinical entity is recognized as CSA or Cervical spondylotic amyotrophy.

Cervical spondylotic amyotrophy is the clinical syndrome in cervical spondylosis characterized by severe muscular atrophy in the upper extremities, with an absent or insignificant sensory deficit. Pathophysiology of this particular syndrome has not been well understood. However, pathophysiology of this syndrome may be multisegmental damage to the anterior horns caused by dynamic cord compression, possibly through circulatory insufficiency (2). Abnormal venous circulation within the cord may cause the selective involvement of the gray matter (3).

Signs/symptoms:

1. Unilateral muscle weakness and atrophy in the deltoid and biceps muscles (1).
2. Very little/insignificant or no significant sensory deficit (2).
3. Age of onset 30-60 years (3)
4. Men were more frequently affected than women (3).

Why the sensory component is not affected in CSA?
According to Kaneko & colleagues; Pathophysiologic feature of CSA involves longitudinal gray matter lesion. Further, less damage to the lateral posterior column is the reason for the preservation of sensory function in the patients especially with distal-type cervical spondylotic amyotrophy.

The Deltoid in CSA:

Shinomiya K reported 4 types of neural injury associated with deltoid pareses associated with CSA patients. The first included isolated C5 nerve root lesions; the second, C6 nerve root lesions; the third, both C5 and C6 nerve root liaisons, and finally, intrinsic pathology.

2 types of CSA according to presentation:

Weakness and atrophy without prominent sensory changes were started from the proximal muscles are proximal type, and from the distal muscles distal type (3).
Distal type patients often presented cold paresis and/or postural finger tremor, which occasionally was the initial symptom. Distal type patients usually do not have extension of atrophy to the proximal muscles during a long course of their illness. But patients of proximal type may have muscular atrophy extended to the distal end. Most patients of proximal type had neurogenic changes on electromyography extended to the distal muscles (3).

2 types of CSA basing on Radiological pathology (5):

Basing on multiple radiological modalities CSA patients were divided into 2 pathologic types;
Type I: The first showed focal bony spur and disc herniation with axial cord rotation and nerve root compression
Type II: The second type demonstrated ventral cord flattening.

Neuroradiological examination:

As revealed on neuroradiological examinations by various authors the compressive paththology can involve anterolateral spinal cord compression or ventral root compression at the C4-5 and C5-6 spaces (1).
Proximal type CSA patients had a cord atrophy at C4/5 intervertebral level, and distal type had cord atrophy at C5/6,6/7. Hence the responsible lesion for the cervical spondylotic amyotrophy is in anterior horn at C5-T1 cord level for the proximal type, and at C7-T1 for the distal type (3).
CSA with intramedullary lesion Fujiwara has demonstrated a case study of a patient who showed severe wasting of the left triceps muscle without any sensory disturbance or long tract sign. A delayed (6 hours) CT scan after intrathecal injection of metrizamide revealed intramedullary left anterior horn cavitation or cystic necrosis. Thus Fujiwara was the first author to report a case of cervical spondylotic amyotrophy, in which intramedullary lesion was confirmed only at the affected side of the spinal cord (4).

Electrophysiologic studies in CSA:

These studies include evoked spinal potentials, motor evoked potentials, and evoked muscle action potentials. Usually Motor evoked potentials, recorded epidurally from the ventral aspect of the thecal sac and the nerve root are clinically significant in diagnosis of CSA.

EMG in distal type of CSA: Kaneko K reported attenuation of postsynaptic potentials with preserved presynaptic potentials at C4-C5, C5-C6, and C6-C7 was characteristic in the evoked spinal cord potentials after median nerve stimulation. The amplitude of the evoked spinal cord potentials after median nerve stimulation was preserved at C2-C3. Further these features implies that lateral posterior column in the spinal cord had less or no involvement in distal-type cervical spondylotic amyotrophy.

Differential diagnosis:

ALS (amyotrophic lateral scelerosis) poses a diagnostic challenge in Cervical spondylosis complicated by CSA.according to Sindo K et al muscle sympathetic nerve activity (MSNA) is the point of differentiation between cervical spondylotic amyotrophy (CSA) and amyotrophic lateral sclerosis (ALS) with cervical spondylosis (CS). During head-up tilting, changes in BP and MSNA were significantly less in patients with ALS than in patients with other subjects. MSNA at rest clearly differentiated CSA from ALS with CS.

Surgical Outcomes:

MORI Kentaro et al reported of 2 the patients surgically treated; one had good recovery of motor strength and the other had moderate recovery despite persistent motor atrophy. These authors have concluded that surgical intervention is effective in patients with CSA despite severe muscle atrophy unless MR imaging shows the presence of severe degenerative intramedullary lesion.
Kunihiko S et al retrospectively investigated the surgical outcomes and radiographically documented changes after microsurgical posterior foraminotomy with en bloc laminoplasty in patients with cervical spondylotic radiculo-myelopathy (CSRM), including cervical spondylotic amyotrophy (CSA), during a period greater than 2 years. This procedure yielded outstanding results both in CSRM & CSA.

References:
1. MORI Kentaro et al; Neurologia medico-chirurgica 46(7) pp.366-370 20060715 (The Japan Neurosurgical Society )
2. Kameyama, Takashi; Spine: 15 February 1998 - Volume 23 - Issue 4 - pp 448-452, Diagnostics
3. Tsuboi Y et al; Rinsho Shinkeigaku. 1995 Feb;35(2):147-52.
4. Fujiwara, Keiju; Spine; 15 May 2001 - Volume 26 - Issue 10 - pp E220-E222, Case Reports
5. Shinomiya K; Spine: January 1994 - Volume 19 - Issue 1
6. Kaneko K; Spine, 1 May 2004 - Volume 29 - Issue 9 - pp E185-E188, Case Report
7. Sindo K et al; Amyotroph Lateral Scler Other Motor Neuron Disord. 2002 Dec;3(4):233-8.
8. Kunihiko S; Journal of neurosurgery, August 2006 Volume 5, Number 2



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