Multiple sclerosis and amyotrophic lateral sclerosis: is there an association or a red flag? A case report and literature review.

Background: Multiple sclerosis (MS) is an inflammatory disease of the central nervous system that causes damage to the myelin and axons and is caused by genetic or environmental factors. Amyotrophic lateral sclerosis (ALS) is characterized by rapidly progressive degeneration of the motor neurons resulting in the presence of upper and lower motor-neuron signs and symptoms.

Case presentation: A 46-year-old female patient presented with symmetrical weakness of the lower limbs and numbness that developed over weeks. Magnetic resonance imaging (MRI) of the brain exhibited typical demyelination features, high signal abnormality involving the periventricular and subcortical white matter, and an oval-shaped lesion. The patient was diagnosed with MS based on the clinical presentation and radiological examination. However, there was rapid progression of the symptoms, involvement of bulbar dysfunction, and muscle atrophy. Furthermore, the patient did not respond to acute therapy and immunotherapy, which made the diagnosis of MS less likely or suggested that it could be associated with another diagnosis. Her neurophysiological test met the criteria of ALS, and she was started on riluzole.

Literature review: We reviewed all articles from 1986 to 2023, and there were 32 reported cases describing the co-occurrence of ALS and MS in different populations. Our case is the 33rd, and to our knowledge, it is the only case reported in the Middle East and specifically in Saudi Arabia. The main proposed mechanism according to postmortem examinations is a combination of degenerative and inflammatory processes with a cascade of production of reactive oxygen species and nitric oxide, which lead to cell death and apoptosis during concomitant ALS with MS.

Conclusion: The co-occurrence of ALS and MS is extremely rare, but it can be explained by pathogenesis related to neurodegeneration, inflammation, or genetic susceptibility. Rapid progressive motor and bulbar symptoms could be red-flag symptoms, extensive evaluation might be needed for these patients.