Apparent diffusion coefficients distinguish amyotrophic lateral sclerosis from cervical spondylotic myelopathy.

Objective: Fifty percent of patients with amyotrophic lateral sclerosis (ALS) have cervical spondylotic myelopathy (CSM) as a complication. Because patients with ALS do not develop bulbar signs and symptoms at onset, differentiating them from patients with CSM is sometimes difficult. We aimed to determine whether the apparent diffusion coefficients (ADCs) of intracranial corticospinal tracts can be used to distinguish between patients with ALS and those with CSM.

Methods: We evaluated 19 consecutive patients with ALS who did not have CSM by cervical MRI, 16 patients with CSM, and 11 healthy controls. We examined the mean ADCs in the precentral gyrus, the corona radiata, the posterior limbs of the internal capsule (PLIC), and the cerebral peduncle by 3T magnetic resonance imaging (MRI). The mean ADCs in the intracranial corticospinal tracts in patients with ALS were compared with those in patients with CSM.

Results: The mean ADCs in the intracranial corticospinal tracts in patients with ALS were compared with those in patients with CSM (p<0.05). Additionally, the mean ADCs in the precentral gyrus, the PLIC, and the cerebral peduncle in the patients with ALS, including the patients who were initially diagnosed as having clinically possible ALS on the basis of the revised El Escorial criteria and did not develop bulbar symptoms at onset, were also higher than those in patients with CSM (p<0.05).

Conclusions: Elevated ADCs in the intracranial corticospinal tracts might be useful for distinguishing ALS from CSM in the early stage of the disease.