Background Many medically-refractory trigeminal neuralgia patients are non-responders to surgical treatment. Few studies have explored how trigeminal nerve characteristics relate to surgical outcome, and none have investigated the relationship between subcortical brain structure and treatment outcomes. Methods We retrospectively studied trigeminal neuralgia patients undergoing surgical treatment with microvascular decompression. Preoperative magnetic resonance imaging was used for manual tracing of trigeminal nerves and automated segmentation of hippocampus, amygdala, and thalamus. Nerve and subcortical structure volumes were compared between responders and non-responders and assessed for ability to predict postoperative pain outcome. Results In all, 359 trigeminal neuralgia patients treated surgically from 2005–2018 were identified. A total of 34 patients met the inclusion criteria (32 with classic and two with idiopathic trigeminal neuralgia). Across all patients, thalamus volume was reduced ipsilateral compared to contralateral to the side of pain. Between responders and non-responders, non-responders exhibited larger contralateral trigeminal nerve volume, and larger ipsilateral and contralateral hippocampus volume. Through receiver-operator characteristic curve analyses, contralateral hippocampus volume correctly classified treatment outcome in 82% of cases (91% sensitive, 78% specific, p = 0.008), and contralateral nerve volume correctly classified 81% of cases (91% sensitive, 75% specific, p < 0.001). Binomial logistic regression analysis showed that contralateral hippocampus and contralateral nerve volumes together classified outcome with 84% accuracy (Nagelkerke R2 = 65.1). Conclusion Preoperative hippocampal and trigeminal nerve volume, measured on standard clinical magnetic resonance images, may predict early non-response to surgical treatment for trigeminal neuralgia. Treatment resistance in medically refractory trigeminal neuralgia may depend on the structural features of both the trigeminal nerve and structures involved in limbic components of chronic pain.

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OBJECTIVEDiffusion tensor imaging (DTI) tractography is commonly used in neurosurgical practice but is largely limited to the preoperative setting. This is due primarily to image degradation caused by susceptibility artifact when conventional single-shot (SS) echo-planar imaging (EPI) DTI (SS-DTI) is acquired for open cranial, surgical position intraoperative DTI (iDTI). Readout-segmented (RS) EPI DTI (RS-DTI) has been reported to reduce such artifact but has not yet been evaluated in the intraoperative MRI (iMRI) environment. The authors evaluated the performance of RS versus SS EPI for DTI of the human brain in the iMRI setting.METHODSPre- and intraoperative 3-T 3D T1-weighted and 2D multislice RS-iDTI (called RESOLVE [readout segmentation of long variable echo-trains] on the Siemens platform) and SS-iDTI images were acquired in 22 adult patients undergoing intraaxial iMRI resections for suspected low-grade glioma (14; 64%), high-grade glioma (7; 32%), or focal cortical dysplasia. Regional susceptibility artifact, anatomical deviation relative to T1-weighted imaging, and tractographic output for surgically relevant tracts were compared between iDTI sequences as well as the intraoperative tract shifts from preoperative DTI.RESULTSRS-iDTI resulted in qualitatively less regional susceptibility artifact (resection cavity, orbitofrontal and anterior temporal cortices) and mean anatomical deviation in regions most prone to susceptibility artifact (RS-iDTI 2.7 ± 0.2 vs SS-iDTI 7.5 ± 0.4 mm) compared to SS-iDTI. Although tract reconstruction success did not significantly differ by DTI method, susceptibility artifact–related tractography failure (of at least 1 surgically relevant tract) occurred for SS-iDTI in 8/22 (36%) patients, and in 5 of these 8 patients RS-iDTI permitted successful reconstruction. Among cases with successful tractography for both sequences, maximal intersequence differences were substantial (mean 9.5 ± 5.7 mm, range −27.1 to 18.7 mm).CONCLUSIONSRS EPI enables higher quality and more accurate DTI for surgically relevant tractography of major white matter tracts in intraoperative, open cranium neurosurgical applications at 3 T.

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Background Medically-refractory trigeminal neuralgia (TN) can be treated successfully with operative intervention, but a significant proportion of patients are non-responders despite undergoing technically successful surgery. The thalamus is a key component of the trigeminal sensory pathway involved in transmitting facial pain, but the role of the thalamus in TN, and its influence on durability of pain relief after TN surgery, are relatively understudied. We aimed to test the hypothesis that variations in thalamic structure and metabolism are related to surgical non-response in TN. Methods We performed a longitudinal, peri-operative neuroimaging study of the thalamus in medically-refractory TN patients undergoing microvascular decompression or percutaneous balloon compression rhizotomy. Patients underwent structural MRI and MR spectroscopy scans pre-operatively and at 1-week following surgery, and were classified as responders or non-responders based on 1-year post-operative pain outcome. Thalamus volume, shape, and metabolite concentration (choline/creatine [Cho/Cr] and N-acetylaspartate/creatine [NAA/Cr]) were evaluated at baseline and 1-week, and compared between responders, non-responders, and healthy controls. Results Twenty healthy controls and 23 patients with medically-refractory TN treated surgically (17 responders, 6 non-responders) were included. Pre-operatively, TN patients as a group showed significantly larger thalamus volume contralateral to the side of facial pain. However, vertex-wise shape analysis showed significant contralateral thalamus volume reduction in non-responders compared to responders in an axially-oriented band spanning the outer thalamic circumference (peak p = 0.019). Further, while pre-operative thalamic metabolite concentrations did not differ between responders and non-responders, as early as 1-week after surgery, long-term non-responders showed a distinct decrease in contralateral thalamic Cho/Cr and NAA/Cr, irrespective of surgery type, which was not observed in responders. Conclusions Atrophy of the contralateral thalamus is a consistent feature across patients with medically-refractory TN. Regional alterations in preoperative thalamic structure, and very early post-operative metabolic changes in the thalamus, both appear to influence the durability of pain relief after TN surgery.