Background Spinal schwannomas are common benign spinal tumors. Their treatment has significantly evolved over the years, and preserving neurological functions has become one of the main treatment goals together with tumor resection. Study Design and Aims Retrospective review focused on clinical assessment, treatment techniques, and outcomes. Methods A retrospective study on our surgical series was performed. Clinical and operative data were analyzed. In regard to neurophysiologic monitoring, patients were retrospectively divided into two groups comparing the outcomes before and after introduction of routine intraoperative neurophysiology tests. Results From 1951 to 2010, 367 patients overall were treated. Diagnosis was obtained using angiography and/or myelography (pre-CT era), MRI, or CT scan. A posterior spinal approach was used for most patients; complex approaches were adopted for treatment of giant/dumbbell tumors. A trend of neurophysiology monitoring decreasing the rate of post-op neurological deficits was observed but was not statistically significant enough to draft evidence-based conclusions. Conclusions Clinical and radiological assessment of spinal schwannomas has markedly changed over the course of 50 years. Diagnostic tools have improved, and detection of recurrence has become way more sensitive. Neurophysiologic monitoring has become a useful intraoperative tool to guide resection and prevent post-op neurological impairment.

The physiological mechanisms underlying the lengthening of the silent period (SP) evoked in active upper limb muscles by repetitive transcranial magnetic stimulation (rTMS) of the motor areas were studied in normal subjects. rTMS was delivered at frequencies of 1 Hz, 2 Hz, 3 Hz, 5 Hz, 10 Hz and 15 Hz and at an intensity just above the motor threshold (Mth). Trains delivered at 2 Hz, 3 Hz, 5 Hz, 10 Hz and 15 Hz significantly prolonged the cortical SP, whereas stimuli at 1 Hz did not. The first few stimuli in the train already prolonged the duration of the cortical SP: the other stimuli did not prolong it further. Motor evoked potentials remained unchanged in amplitude regardless of the frequencies and number of stimuli in the train. The effect of intensity of stimulation was studied by delivering trains at suprathreshold intensity (110% and 140% of Mth) and 3-Hz frequency and with trains at subthreshold intensity and 5-Hz and 10-Hz frequencies. SPs had a longer duration at 140% than at 110% Mth intensity. SPs elicited by 3-Hz trains at 140% and 110% Mth intensity lengthened to a similar extent over the course of the train. rTMS delivered at an intensity below Mth did not evoke cortical SPs over the course of the trains. Repetitive stimulation of the cortical forearm motor areas prolonged the duration of the cortical SP in forearm flexor muscles but failed to evoke SPs in the biceps muscles. The maximal single stimulus intensity and less intense stimuli delivered in short trains evoked SPs of similar duration. We propose that rTMS delivered in trains at frequencies higher than 1 Hz and at suprathreshold intensity prolongs the cortical SP mainly through temporal summation of inhibitory interneurones.

The effects of repetitive transcranial stimulation (rTMS) on brain activity remain unknown. In healthy subjects, we studied the effects of rTMS on the duration of the cortical silent period (SP). Repetitive stimuli were delivered with a Cadwell High Speed Magnetic Stimulator and a figure-of-eight coil placed over the hand motor area. rTMS was delivered in trains of 11 or 20 stimuli at frequencies of 3 and 5 Hz and at stimulation intensities of 110 and 120% of motor threshold. The SP was recorded from the forearm muscles during a voluntary contraction (20% of maximum effort). rTMS delivered at a frequency of 3 and 5 Hz and intensities of 110 and 120% motor threshold prolonged the duration of the SP, without modifying either the size or the latency of the muscle-evoked potentials (MEP). A conditioning train of 11 stimuli at 3 Hz had no effect on the duration of the SP evoked by a single magnetic shock delivered 600 ms after the train. These findings show that rTMS increases the duration of the cortical SP, but does so only during the train of stimuli. rTMS probably changes the duration of the SP by facilitating cortical inhibitory interneurons.

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