Spinal Surgery and ALS
Spinal Surgery and ALS
Abstract & Commentary
By Michael Rubin, MD, Professor of Clinical Neurology, NewYork-Presbyterian Hospital, Cornell Campus. Dr. Rubin is on the speaker's bureau for Athena Diagnostics, and does research for Pfizer and Merck.
Synopsis: A small but significant number of patients with unrecognized ALS undergo spinal surgery that in retrospect may be inappropriate.
Source: Yoshor D, et al. Incidence and Characteristics of Spinal Decompression Surgery After the Onset of Symptoms of Amyotrophic Lateral Sclerosis. Neurosurgery. 2005;57:984-989.
Spondylosis and amyotrophic lateral sclerosis (ALS) affect patients of similar age and can mimic each other clinically. Magnetic resonance imaging (MRI) of the spine, when normal, will indicate when surgery is unwarranted in a patient suspected of having ALS. When spinal MRI demonstrates spondylosis with or without compression, as it may in over 60% of motor neuron disease patients, surgery becomes a therapeutic option, and judgement must be exercised to decide who goes under the knife. At other times, spondylosis is diagnosed in patients unsuspected of having ALS, only to have them deteriorate and declare themselves subsequently. How often does this occur?
Among over 1500 patients in the Baylor Muscular Dystrophy Association database with motor neuron disease, 1131 had typical ALS, satisfying El Escorial/Airlie House criteria. Of these, 47 (4.2%) had undergone spinal surgery prior to the eventual correct diagnosis of ALS, of which 8 (17%) underwent a second additional operation. Cervical surgery comprised the largest group (56%), including laminectomy and discectomy/corpectomy, followed by lumbar laminectomy or discectomy (42%) and thoracic laminectomy (2%). No improvement was noted in 86%, with an additional 9% experiencing small or possible improvement. Only 2 patients (4%) truly initially benefited from surgery, though they also progressed to ALS.
For the most part, no significant differences could be ascertained to separate those ALS patients who unwittingly underwent surgery from those that did not, including age at diagnosis, disease severity at time of final diagnosis, as measured by the Appel ALS (AALS) score, mean (presumed) rate of disease progression prior to or following final diagnosis, respiratory slope of decline, or male gender. Bulbar symptoms were significantly more common in the non-surgical group, presumably because the localization of these symptoms precluded a spinal etiology, and a final diagnosis of ALS was made significantly later in the surgical group, relative to symptom onset, compared to the nonsurgical group, presumably because surgery did not color the thinking of the treating physicians. Overall survival, based on Kaplan-Meier curves, was not different between the 2 groups. ALS should be considered in the differential diagnosis, and work-up of any patient with spondylosis being considered for surgery.
Commentary
Given the confusion that spondylosis causes in diagnosing amyotrophic lateral sclerosis (ALS), what might be done to secure the correct diagnosis and prevent unnecessary spinal surgery in these patients? Several indices, measured by diffusion-tensor magnetic resonance imaging (MRI) of the corticospinal tract, including mean diffusivity, fractional anisotropy, and eigen values, may hold the answer (Cosottini M, et al. Radiology. 2005:237:258-264). Eighteen ALS patients, 8 progressive muscular atrophy (PMA) patients, and 12 controls underwent diffusion-tensor MRI to determine if these studies distinguish patients from controls. Statistical analysis included Mann-Whitney testing and Pearson and Spearman rank correlation testing. Compared to normal subjects, mean diffusivity was significantly increased and fractional anisotropy significantly decreased in ALS patients; the former correlating with disease duration, the latter with disease severity. PMA patients showed no significant change. Diffusion orthogonal to fiber tracts was increased only in ALS, while diffusion along fiber tracts was normal in all patients. Diffusion-tensor MRI of the corticospinal tract differentiates ALS from PMA and normals and provides useful information in the workup of ALS patients. Where spondylosis muddles the clinical picture, tensor study may clear the waters. Further study of this modality will be welcome.
A small but significant number of patients with unrecognized ALS undergo spinal surgery that in retrospect may be inappropriate.Subscribe Now for Access
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