New insights into the trigeminal nerve somatotopy: Lessons from partial sensory rhizotomy

Abstract

Background Trigeminal neuralgia (TN) is a severe unilateral facial pain involving one or more branches of the trigeminal nerve (V). Microvascular decompression is a standard curative treatment of pharmacoresistant TN. Alternative procedures used for secondary or idiopathic TN usually lead to a high rate of pain recurrence and sensitive deficits. Objective To study a retrospective cohort of patients treated by partial sensory rhizotomy (PSR) and to precise a somatotopy of the V. Methods Consecutive cases of adult patients treated in our institution between March 2000 and June 2015 for pharmacoresistant TN without vascular compression by two-thirds pars major rhizotomy of the V were retrospectively collected. Results Among 155 patients treated for TN in our institution, 22 patients that had undergone PSR were included. Fourteen patients had idiopathic TN without compression of the nerve root, 6 had TN due to multiple sclerosis and 2 had trigeminal conflict by Meckel's cave inoperable tumor. Complete pain relief was achieved in 86.4%. Partial and focalized postoperative hypoesthesia was present in 22.7%. TN recurrence rate at 5 years was 31.5% (SD 10.9%). The variability of sensory loss and pain relief after PSR are discussed in the light of somatotopy of the V. Conclusions Based on our results, we conclude that a rhizotomy of the ventrolateral two-thirds of pars major of the V is a safe and effective alternative to other destructive procedures to treat pharmacoresistant TN without vascular compression, and we clarify the functional somatotopy of the V at the juxtapontine region.