Transcranial magnetic and electric stimulation discriminates Bell's palsy from neuroborreliosis in children- a pilot trial

Objectives: This study aims to investigate the diagnostic aspects of transcranial magnetic stimulation (TMS) in addition to electric stimulation in acute facial paralysis in children. Canalicular hypoexcitability on the affected side is considered as a specific finding which discriminates Bell's palsy from neuroborreliosis .

Material and Methods: We examined 14 patients (median age 11.5, range 4.6–17.5 y) with peripheral facial nerve palsy (Bell's palsy: n=8; Lyme disease: n=6, 1 bilateral affection). Serum and liquor were examined for antibodies against Borrelia burgdorferi. Liquor cell count, glucose and protein content were measured. Normal values for facial nerve conduction times were obtained in 10 healthy subjects (median age 10.1 y, range 5–15 y). The facial nerve was electrically stimulated at the foramen stylomastoideum and magnetically in its proximal canalicular segment. TMS was performed by ipsilateral parieto-occipital placement of coil. Corresponding electromyographic recordings were obtained from the ipsilateral M. mentalis with surface electrodes.

Results: The average grade of palsy did not differ significantly between the two disorders (Bell's palsy: mean range 3±0.66/5, Lyme disease: mean range 3.1±0.75/5). The electrophysiologic assessment was performed 2–4 days (mean range 2.8±1.1d) after the onset of symptoms. All patients with Bell's palsy showed a significant decrease in the MEP amplitude after canalicular magnetic stimulation compared to their unaffected facial nerve (p=0.001) as well as compared to the healthy control group (p=0.03). The group with pleocytosis and/or positive serologic findings for Borrelia burgdorferi, in contrast, had not significant difference.

Conclusions: The neurophysiologic assessment of the facial nerve with electric and transcranial stimulation is a valid diagnostic method in children. In addition to conventional serologic and cytologic findings it allows to differentiate Bell's palsy from neuroborreliosis. Giving an immediate result, it supports the therapeutic decision whether the use of antibiotics is indicated or not.