Objective: Acute transverse myelitis is a relatively rare, frequently debilitating but potentially treatable emergency. The objective of this study was to evaluate the incidence and etiology of acute transverse myelitis in two major hospital districts in Southern Finland.

Methods: We identified all patients with acute transverse myelitis admitted to Turku University Hospital and Päijät-Häme Central hospital during nine years. The two hospitals serve a catchment area of 673,000 people in Southern Finland. Acute transverse myelitis was diagnosed according to the 2002 Transverse Myelitis Consortium Working Group. Patient files were reviewed for details of the clinical presentation and disease outcome, for laboratory findings and for neuroimaging. Charts were re-evaluated after an average of 7.7 years for confirmation of the acute transverse myelitis etiology.

Results: In total 63 patients fulfilled the Transverse Myelitis Consortium Working Group diagnostic criteria for acute transverse myelitis. The frequency of the condition was hence 1.04 cases/ 100,000 inhabitants/ year. In the studied cohort, 7/63 (11%) patients had idiopathic transverse myelitis after initial evaluation and in 4/63 (6.3%) patients the idiopathic transverse myelitis remained the final diagnosis after follow-up and re-evaluation. Of the disease-associated myelitis cases MS or clinically isolated syndrome was the largest group, explaining 41% of all myelitis cases. The mean follow-up time before a patient was diagnosed with MS was 1.7 ± 2.2 years. Other etiologies included acute disseminated encephalomyelitis (ADEM), neurosarcoidosis, neuromyelitis optica (NMO), systemic autoimmune diseases and infectious diseases.

Conclusions: In more than half of the acute transverse myelitis cases the final diagnosis is other than MS. Careful diagnostic work-up is needed for correct early treatment and best long-term outcome.