STRUCTURAL AND METABOLIC MRI TO CHARACTERIZE THE RESPONSE TO SURGERY IN TRIGEMINAL NEURALGIA
Creators: Danyluk, Hayden J.
Publisher: name: University of Alberta Library
Year: 2023

<p>Trigeminal Neuralgia (TN) is a chronic, neuropathic, facial pain condition characterized by severe unilateral pain attacks, electric shock-like or shooting in character, confined to regions of the face innervated by the trigeminal nerve (the fifth cranial nerve, CNV). TN is commonly associated with neurovascular compression of CNV, but may also be idiopathic or occur secondary to other diseases. While the underlying pathophysiology of TN is incompletely understood, it is widely believed that CNV microstructure (specifically myelination) is affected in patients with this condition. TN is treated initially with medications used for neuropathic pain, but many TN patients become medically refractory, at which point various CNV-directed surgical options may be offered. Even with the most effective surgical treatment, a considerable proportion of TN patients are initial non-responders or experience early pain recurrence. Currently, surgical treatment resistance in TN is poorly understood. <br>
In order to better understand surgical treatment resistance in TN, we proposed the use of magnetic resonance imaging (MRI) to perform an in-depth analysis of both CNV and brain features in patients with TN. The main aims of this thesis were: 1) to develop a novel, nerve-specific MRI acquisition protocol permitting more accurate characterization of CNV microstructure in TN; 2) to identify, using MRI, preoperative structural and metabolic CNV and brain abnormalities in TN patients, and to characterize changes in these features occurring longitudinally following surgical treatment; and 3) to examine the differences between responders and non-responders to surgical treatment for TN using imaging-based CNV and brain features.<br>
Our newly developed nerve-specific MRI protocol more accurately characterized CNV microstructure than others used previously. In contrast to previously published studies, we did not detect clear preoperative CNV microstructural abnormalities in patients with TN, although contralateral thalamus volume was increased. There were also no preoperative differences in CNV microstructure between surgical responders and non-responders, although, contralateral CNV volume was increased. Furthermore, the hippocampus was comparatively enlarged and thalamus shape was different in non-responders. In the early postoperative period (&lt;1-week), divergent changes in thalamic metabolism were observed between responders and non-responders even though CNV microstructure was not appreciably different. </p>

<p>In summary, this thesis provides novel evidence that brain and nerve structural features may distinguish responders to TN surgery from non-responders preoperatively. Additionally, while CNV microstructural changes occur following surgery, our data suggest that these are less able to explain differences in surgical response, which instead may relate to variable metabolic effects of surgery between responders and non-responders. Thus, perioperative assessment utilizing multimodal MRI may provide insight into the underlying pathophysiology of TN as well as therapeutic mechanisms of surgical treatment.  </p>