Case Diagnosis: Amyotrophic Lateral Sclerosis
Case Description: 35 year-old female with a 7-year history of Chronic Myeloid Leukemia in remission on Imatinib, who presented with frequent falls. She initially developed muscle spasms and stiffness, which progressed to weakness of left lower, then right lower, followed by left upper extremity. An anterior truncal sensory level involvement at Right T2 and Left C3 segment was found. Blood and CSF studies were unremarkable. MRI revealed nonspecific foci of T2/FLAIR signal hyperintensity in the bilateral subcortical white matter. Differential diagnosis included neural invasion of CML, tyrosine kinase inhibitor toxicity, and ALS. EMG showed diffuse motor neuron pathology but did not have giant MUAPs with reduced recruitment seen in ALS. She was treated with plasmapheresis and IVIG with no improvement in symptoms. Sural nerve biopsy was scheduled, however, the patient suffered cardiac arrest while undergoing anesthesia and the procedure was aborted. After recovering she refused to undergo the procedure again.
Discussions: The progression of her motor symptoms are typical of ALS although her EMG studies were not definitive. However, sensory findings are not typically found in ALS. Diffuse leptomeningeal disease from recurrence of CML and Imatinib toxicity, although typically sensorimotor, were both not excluded by the EMG. A workup of ruling out all other possible causes eventually led to the diagnosis of ALS. The atypical presentation in this case may be related to her underlying CML. Some studies have suggested that ALS is a paraneoplastic syndrome and its incidence is increased in certain malignancies.
Conclusions: ALS is a rare disease, of which there is still much to be discovered. It is important to keep ALS in the differential diagnosis of patients with progressive weakness, even with non-definitive EMG studies, especially in patients with a history of cancer.