TICK-BORNE ENCEPHALITIS IN SWEDEN IN RELATION TO ASEPTIC MENINGOENCEPHALITIS OF OTHER ETIOLOGY - A PROSPECTIVE-STUDY OF CLINICAL COURSE ANDOUTCOME

A total of 149 patients with clinical symptoms of acute viral meningo- encephalitis were enrolled in this study from June 1991 to December 19 93. Tick-borne encephalitis (TEE) was diagnosed in 85 of the 149 patie nts (males 54%, median age 42 years (range 15-78)). The initial clinic al appearance of TEE was classified as mild (mainly meningeal; (n = 47 ), moderate (n = 31) or severe (n = 7), more or less encephalitic. The most common acute symptoms of encephalitis were ataxia (26%), altered consciousness (20%), decreased concentration or memory (9%), irritabl e response to light and sound (28%), tremor (9%) and dysphasia (9%). S pinal nerve paralysis (11%) occurred in all three clinical stages and did not correlate with the severity or duration of encephalitis. The d uration of hospitalisation, the time on the sick-list and the time to recovery were significantly longer in TEE patients. All patients survi ved, but many patients with TEE suffered an extended period of neurolo gical dysfunction. Of patients with TEE 80% (68/85) showed persisting symptoms of CNS dysfunction on follow-up at week 6, compared with 55% (35/64) of the patients with aseptic meningitis of other aetiology. Th e corresponding figures after 1 year were 40% (33/83) and 20% (13/64). One year after TEE 13 (28%) patients with initially mild, meningeal s ymptoms had decreased memory and decreased concentration capacity, dys phasia or ataxia. Spinal nerve paralysis persisted after 1 year in 5 o f 9 patients with TEE. In conclusion, TEE in Sweden is associated with a significant morbidity and a post-TEE syndrome existed after 1 year in more than one third of the patients.