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03.02.2018 | Original Article - Neurosurgical Techniques | Ausgabe 5/2018

Acta Neurochirurgica 5/2018

The timing of stereotactic radiosurgery for medically refractory trigeminal neuralgia: the evidence from diffusion tractography images

Zeitschrift:
Acta Neurochirurgica > Ausgabe 5/2018
Autoren:
Cheng-Chia Lee, Shin Tai Chong, Ching-Jen Chen, Sheng-Che Hung, Huai-Che Yang, Chung-Jung Lin, Chih-Chun Wu, Wen-Yuh Chung, Wan-Yuo Guo, David Hung-Chi Pan, Hsiu-Mei Wu, Jason P. Sheehan, Ching-Po Lin
Wichtige Hinweise

Comments

The authors report on careful DTI studies of trigeminal nerves in trigeminal neuralgia patients treated with radiosurgery. Of special interest to me was the difference in fractional anisotropy between short-term and long-term trigeminal patients that may reflect the extent of myelin damage. Clinical correlation of DTI parameters with the extent of nerve damage may allow for better prediction of outcome in various therapeutic procedures. Serial fractional anisotropy changes in the imaged trigeminal root over time could also optimize the time window for intervention.
DTI is a novel tool in the evaluation of cranial nerve pathology but hints of intriguing possibilities in improving patient follow-up and care.
Zvi Harry Rappaport
Petah Tiqvah, Israel

Abstract

Background

Diffusion tensor imaging (DTI) is a novel MRI technique that enables noninvasive evaluation of microstructural alterations in white matter of brain. Initially, DTI was used in intra- or inter-hemispheric association bundles. Recent technical advances are overcoming the challenges of imaging small white matter bundles, such as the cranial nerves. In this study, we use DTI to shed more light on the microstructure changes in long-standing trigeminal neuralgia. We also utilize DTI to study the effect of early stereotactic radiosurgery (SRS) on the microstructures of the trigeminal nerve and to predict the effectiveness of early SRS in the treatment of medically refractory trigeminal neuralgia (TN).

Methods

To analyze the presentation of trigeminal nerve, the DTI was reconstructed in 21 cases pre- and post-SRS. DTI parameters recorded include fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), axial diffusivity (AD), linear anisotropy coefficient (Cl), planar anisotropy coefficient (Cp), and spherical anisotropy coefficient (Cs). Comparisons between ipsilateral (symptomatic) and contralateral (asymptomatic) trigeminal nerves and symptom durations of < 5 and ≧ 5 years were performed.

Results

The study cohort comprised 21 patients with TN with a median age of 66 years. Initial adequate facial pain relief (Barrow Neurological Institute facial pain scores I–IIIb) was achieved in 16 (76%) patients. For the pre-SRS DTI findings, ipsilateral trigeminal nerve was associated with higher baseline root entry zone (REZ) Cs compared to contralateral nerve (0.774 vs. 0.743, p = 0.04). Ipsilateral trigeminal nerve with symptoms of < 5 years was associated with higher baseline FA compared to trigeminal nerve with symptoms of ≧ 5 years (0.314 vs. 0.244, p = 0.02). For the post-SRS DTI findings, ipsilateral trigeminal nerves with symptoms of <5 years demonstrated decrease in Cl, while those with symptoms ≧ 5 years demonstrated increase in Cl after SRS at the ipsilateral REZ (− 0.025 vs. 0.018, p = 0.04). At the cisternal segment of ipsilateral trigeminal nerve, symptoms of < 5 years were associated with decreased FA and increased λ2, while symptoms of ≧ 5 years were associated with increased FA and decreased λ2 after SRS (FA − 0.068 vs. 0.031, p = 0.04, λ2 0.0003 vs. − 0.0002, p = 0.02).

Conclusions

SRS provides high rates of initial pain relief with moderate rates of facial hypoesthesia. Ipsilateral trigeminal nerve was associated with higher baseline REZ Cs, and baseline FA was associated with duration of symptoms. There were significant associations between duration of symptoms and changes in ipsilateral REZ Cl, cisternal segment FA, and cisternal segment λ2 after SRS. These preliminary findings serve as comparisons for future studies investigating the use of DTI in radiosurgical planning for patients with TN.

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