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Tick borne encephalitis (TBE) virus causes the most important arthropod transmitted disease in central Europe. In endemic areas, TBE has an incidence of 1.2 per 10000 and a mortality of approximately 1%. The TBE virus is a neurotropic human pathogen. The most common presentations are meningitis (49%), meningoencephalitis (41%) and meningoencephalomyelitis (10%).1 Patients with concomitant spinal cord involvement are thought to be affected more severely and mechanical ventilation is often necessary.2
We present an unusual TBE case with an isolated myelitis without signs of meningitis or meningoencephalitis.
A 43‐year‐old man from the Black Forest area, Germany, who had not had TBE vaccination developed symptoms of gastroenteritis with fever (diarrhoea, nausea and vomiting) lasting for approximately 1 week. Two days after recovery from the gastrointestinal symptoms he experienced severe pain in his shoulders followed by proximal pareses of his brachial muscles without signs of meningism. As the symptoms were not ameliorating during the following days, the patient was admitted to hospital. At that time he had severe pareses of the upper extremities and mild pareses of the lower extremities. All tendon reflexes appeared very brisk but pyramidal signs were absent. Sensory testing was normal. The patient recalled a tick bite several weeks ago, after having collected mushrooms in the forest.
The following laboratory findings were abnormal: increased C reactive protein 8 mg/l, leucocytosis 12200/µl, cerebrospinal fluid with mild pleocytosis (49 cells/µl: 80% lymphocytes, 20% monocytes), a clearly increased total protein content (2070 mg/l), local IgM synthesis of 83.5% and an increased IgG index of 0.81. Serological testing of the CSF and serum showed positive IgM and IgG antibody reactivity against TBE virus. A virus specific IgG CSF/serum index of 3.69 (normal value <2) confirmed high intrathecal specific antibody production. Coinfection with Borrelia burgdorferi was excluded. Moreover, there was no evidence of further possible aetiologies, such as infection by Treponema pallidum, herpes simplex virus 1 and 2, varicella zoster virus, enterovirus, HIV, Epstein–Barr virus or cytomegalovirus, or evidence of a vasculitis or collagenosis.
On electromyography and electroneurography, axonal lesions were seen in the left deltoid (C5/6), the left triceps (C7/8) and the left abductor digiti minimi manus (C8/Th1). There was normal neurography of the right and left radial nerve, the left ulnar and the left median nerve, and thus a brachial plexus lesion was excluded. In summary, there was evidence of a polyradiculitic or anterior horn lesion from C5 to Th1 (maximum at C5 and C7).
Motor evoked potentials showed delayed central motor conduction to both legs and the right arm. Tibial somatosensible evoked potentials were pathological on the left side, also with a central delay. The clinical and electrophysiological pattern was compatible with an incomplete myelitis involving the anterior horn cells.
Spinal MRI performed 25 days after symptom onset was normal. To exclude mild encephalitis, cranial MRI and electroencephalography were performed. Both examinations showed normal findings.
The patient recovered slowly and incompletely over the following weeks. The pareses were slightly improved, in particular the pareses in the distal upper extremities. The weakness of the proximal arm muscles remained almost unchanged.
The most frequent symptoms of TBE are meningitis, meningoencephalitis or meningoencephalomyelitis. Polio‐like syndromes with polyradiculitic manifestations can complicate the disease.3,4,5 These reported cases of myeloradiculitis in TBE virus infections, however, showed additional signs of meningoencephalitis or cranial nerve involvement.5 To the best of our knowledge, only one case with an isolated anterior horn lesion of the C3 to the Th1 level has been reported.6 Even in this case, cranial MRI showed two cerebral lesions.
We have presented the second case of a patient with an isolated myelitis caused by a TBE virus infection. In contrast with the patient described by Beer et al,6 our patient not only showed impairment of the anterior horn neurons but also involvement of the descending spinal pathways suggestive of incomplete transverse myelitis. This presumption was supported by the clinical finding of brisk tendon reflexes and a central conduction delay demonstrated by motor evoked potentials. Respiratory muscles were not affected. An additional polyradiculitis cannot be differentiated from an anterior horn lesion by clinical symptoms or electrophysiologically. One argument in favour of a polyradiculitis was the clearly increased total protein in our patient. MRI did not disclose any spinal cord lesion. A low incidence of cerebral or spinal MRI lesions in TBE infection has also been reported elsewhere.1 Thus MRI is of limited value in the diagnosis of TBE.1 This may be explained by the rapid resolution of early T2 hyperintensities. Resolution of MRI lesions despite the limited clinical improvement after 6 weeks has been described by Beer et al.6 This seems to be in contrast with lesions in brain parenchyma in which a good correlation between clinical improvement and restitution of T2 abnormalities has been found.2
This unusual case shows that even in patients presenting with incomplete transverse myelitis without signs of meningitis or meningoencephalitis, a TBE virus infection should be considered as a differential diagnosis.
Competing interests: None.