Amyotrophic Lateral Sclerosis Mimic Syndrome in a 24-Year-Old Man with Chiari 1 Malformation and Syringomyelia: A Clinical Case

Chiari 1 Malformation (CM1) is classically defined as a caudal displacement of the cerebellar tonsils through the foramen magnum into the spinal cord. Modern imaging techniques and experimental studies disclose a different etiology for the development of CM1, but the main etiology factor is a structural defect in the skull as a deformity or partial reduction, which push down the lower part of the brain and cause the cerebellum to compress into the spinal canal. CM1 is classified as a rare disease. CM1 can present with a wide variety of symptoms, also non-specific, with consequent controversies on diagnosis and surgical decision-making, particularly in asymptomatic or minimally symptomatic. Other disorders, such as syringomyelia (Syr), hydrocephalus, and craniocervical instability can be associated at the time of the diagnosis or appear secondarily. Therefore, CM1-related Syr is defined as a single or multiple fluid-filled cavities within the spinal cord and/or the bulb. A rare CM1-related disorder is syndrome of lateral amyotrophic sclerosis (ALS mimic syndrome). We present a unique clinical case of ALS mimic syndrome in a young man with CM1 and a huge singular syringomyelic cyst with a length from segment C2 to Th12. At the same time, the clinical picture showed upper hypotonic-atrophic paraparesis in the absence of motor disorders in the lower extremities. Interestingly, this patient did not have a disorder of superficial and deep types of sensitivity. This made it difficult to diagnose CM1. For a long time, the patient's symptoms were regarded as a manifestation of ALS, as an independent neurological disease, and not as a related disorder of CM1. Surgical treatment for CM1 was not effective, but it allowed to stabilize the course of CM1-related ALS mimic syndrome over the next two years.

Predictors of amyotrophic lateral sclerosis mimic syndrome

The term amyotrophic lateral sclerosis mimic syndrome (ALSms) includes pathologies that present signs or symptoms similar to those caused by amyotrophic lateral sclerosis (ALS), which can lead to misdiagnosis. In general, any kind of misdiagnosis can result in negative clinical, psychological and economic consequences as well diagnostic and treatment delay. The objectives were to determine the frequency and to compare the demographic and clinical characteristics of patients with ALS and ALSms in our ALS clinic. We retrospectively studied all patients evaluated from 2007 to 2017 including only patients with a definite final diagnosis. Out of 368 patients with motor neuron disease symptomatology, 43 (11.7%) had an ALSms. The most frequent etiology was compressive myelopathy (32.6%). Multivariate analysis considering positive associations was statistically significant for patients having only upper or lower motor neuron signs in the physical examination, a non-compatible electromyogram (EMG), as well as atypical first symptoms. ALS misdiagnosis is an ongoing and not infrequent problem. From our series of patients, atypical symptoms, absence of EMG pathological findings or isolated upper or lower motor neuron disease should prompt suspicion of a differential diagnosis.