Trigeminal neuralgia treatment outcomes following Gamma Knife radiosurgery with a minimum 3-year follow-up

Factors Affecting Long-Term Pain Control After Gamma Knife Radiosurgery in Secondary Tumor-Related Trigeminal Neuralgia

BACKGROUND AND OBJECTIVES

Trigeminal neuralgia (TN) can often result from compression of the trigeminal root by various tumors. Although the efficacy of Gamma Knife radiosurgery (GKRS) in treating these tumors is well documented, it remains to be determined if tumor control drives pain relief in tumor-related TN.

METHODS

We retrospectively analyzed all patients who underwent GKRS for secondary TN at our center, recording preoperative clinical and radiological data, and assessing outcomes regarding Barrow Neurological Institute (BNI) pain scores and tumor volume at follow-up. We then analyzed the factors that predicted pain relief, including long-term tumor control.

RESULTS

The mean age of 156 patients (90 women and 66 men) was 52.2 ± 13.9 years. The most frequent pathology was schwannoma (108 cases, 67.9%), followed by meningioma (48 cases, 29.6%). The mean dose of GKRS administered was 12.08 ± 5.5 Gy. The mean follow-up was 49.7 ± 17.1 months. Four patients (2.5%) were lost to follow-up. At latest follow-up, 59 patients (38.8%) achieved complete pain relief (BNI 1), whereas 72 patients (47.4%) achieved adequate pain relief (BNI 2 and 3). Failure of pain relief occurred in 21 patients (13.8%). Multivariate analysis revealed that patients aged younger than 50 years (odds ratio: 6.95, 95% CI: 2, 22.8, P = .001) and increase in tumor volume at follow-up (odds ratio: 40.38, 95% CI: 5.39, 321.45, P < .001) predicted failure of pain relief.

CONCLUSION

GKRS is effective among patients with secondary tumor-related TN, with complete pain relief in 38.8% of patients and adequate pain relief in 47.4%. The most frequent complication is facial hypesthesia, affecting 8.3% of patients. Age ≥50 years and decreased or stable tumor volume significantly predict BNI 1-3 pain relief at the latest follow-up. Although pain relief is linked to long-term tumor control, it is not the sole factor at play.

Single Fraction Radiosurgical Tolerance of Brainstem, Trigeminal Nerve, and Meckel's Cave for Facial Numbness

PURPOSE

This article reviews toxicity outcomes for a series of patients treated with stereotactic radiosurgery for trigeminal neuralgia, focusing on dose to the brainstem, trigeminal nerve, and Meckel's cave as possible explanatory variables for the development of the most common posttreatment neuropathy, facial numbness.

METHODS AND MATERIALS

A retrospective review of 136 cases treated with CyberKnife radiosurgery for trigeminal neuralgia was performed. Dose was initially (cohort 1) prescribed to 57 to 64 Gy covering a 6-mm cylindrical shaped target volume ≥2 mm from the dorsal root entry zone. Subsequently, a deliberate change to isocentric treatment planning occurred, resulting in delivery of 85 Gy to a spherical target (cohort 2). Brainstem, trigeminal nerve, and Meckel's cave were contoured, and a variety of dosimetric and clinical factors were analyzed for association with development of treatment-related facial numbness.

RESULTS

Treatment-related numbness occurred in 59 of 136 (43%) patients and did not differ between the treatment cohorts. Fifty-two patients experienced Barrow Neurological Institute (BNI) grade II toxicity, and 7 patients experienced BNI grade III toxicity. Time to numbness was 16.0 months for cohort 1 and 10.4 months for cohort 2 (P = .184). The median brainstem maximum dose was 26.1 Gy, ranging from 4.2 Gy to 57.3 Gy. Maximum dose to the trigeminal nerve was 85 Gy. Mean trigeminal nerve dose was 47.3 Gy. The median Meckel's cave maximum and mean doses were 26.0 Gy and 6.8 Gy, respectively. No definitive upper limit dose threshold was detected for the structures analyzed, but trends were noted for maximum trigeminal nerve dose of 85 Gy (P = .083) and for prescription dose (P = .057) and trigeminal nerve V40 (P = .077) in the type I subset.

CONCLUSIONS

Brainstem, trigeminal nerve, and Meckel's cave tolerated doses within the range delivered. Discussion of the literature is provided to guide treatment planning and management.

Neuropathic Pain Secondary to Multiple Sclerosis: A Narrative Review

Multiple sclerosis (MS) is a chronic autoimmune disease that affects the central nervous system (CNS). Neuropathic pain in MS is a debilitating symptom that significantly impairs the quality of life for a substantial proportion of MS patients. Neuropathic pain in MS stems primarily from demyelination, axonal loss, CNS inflammation, and direct damage to the myelin sheath, leading to pain manifestations such as ongoing extremity pain, Lhermitte's phenomenon, and trigeminal neuralgia (TN). The pathophysiological mechanisms behind MS-related neuropathic pain are explored in this review, highlighting central sensitization, neural dysfunction, spinal thalamic tract dysfunction, and inflammatory processes that exacerbate neuronal damage. Neuropathic pain in MS necessitates comprehensive assessment tools and neurophysiological tests to differentiate neuropathic pain from other MS symptoms accurately. Treatment strategies for MS-related neuropathic pain encompass pharmacological interventions, including anticonvulsants and antidepressants, and emerging therapies targeting specific inflammatory processes. The review advocates for a holistic approach to management, incorporating innovative treatments and multidisciplinary strategies to address both the physical symptoms and psychosocial aspects of this disorder. This comprehensive overview underscores the importance of ongoing research into targeted therapies to improve patient outcomes and enhance the quality of life for those affected by MS.

Effectiveness, Safety, and Predictors of Response to 5% Lidocaine-Medicated Plaster for the Treatment of Patients With Trigeminal Neuralgia: A Retrospective Study

BACKGROUND

Whether 5% lidocaine-medicated plaster (LMP) is a valuable therapeutic option for the treatment of trigeminal neuralgia (TN) is worth exploring. If LMP is proven effective for TN, positive predictors of the analgesic effects of LMP warrant further investigation.

OBJECTIVE

To evaluate the efficacy and safety of LMP for the treatment of TN, and to explore the predictive factors for the treatment efficacy of LMP.

METHODS

This is a retrospective and observational study. We analyzed the efficacy of LMP for the treatment of TN between March 2019 and January 2022. The follow-up time was approximately 2 weeks, 1 month, 2 months, and 3 months after LMP treatment. The LMP response was considered the Barrow Neurological Institute (BNI) score of I to III and an improvement in BNI of at least I grade from pretreatment baseline. Univariable and multivariable logistic analyses were performed to identify the predictive factors for LMP response.

RESULTS

A total of 103 patients were included and analyzed in this study. LMP was effective in some TN patients, with an efficacy rate of 21.4%, 21.4%, 18.4%, and 16.5% after 2 weeks, 1 month, 2 months, and 3 months of LMP treatment, respectively. The overall adverse event rate associated with LMP was 5.8%, and the reported adverse events were all skin reactions. Facial trigger points (odds ratio [OR] = 0.25, 95% confidence interval [CI] = 0.07-0.86, P = 0.03) and a lower BNI score (OR = 0.37, 95% CI = 0.07-0.87, P = 0.01) were identified as potential predictors for initial efficacy (2-week follow-up) of LMP treatment.

CONCLUSIONS AND RELEVANCE

LMP has been shown to provide effective and sustained analgesia in some TN patients with minimal risk of systemic adverse reactions. Patients with facial trigger points and mild to moderate pain are more likely to benefit from LMP treatment. Our data suggest that LMP may be an effective treatment option for patients with the aforementioned characteristics of TN.

Drilling off the Petrosal Apex and Opening the Upper Wall of Meckel's Cave Are the Key Elements of Good Outcomes in the Treatment of Trigeminal Neuralgia Secondary to Petrous Apex Meningioma

Objective

The surgical management of trigeminal neuralgia (TN) caused by petrous apex meningioma (PAM) is still a challenge because of the lesion’s deep location and the surrounding complex structures. The authors describe the intradural anterior transpetrosal approach (ATPA) and its effect on the treatment of TN secondary to PAM.

Methods

A retrospective analysis of 15 patients with TN secondary to PAM who underwent surgery via the intradural ATPA was conducted. The key techniques, which included drilling off the petrosal apex (PA) and opening the upper wall of Meckel’s cave (MC), are described in detail.

Results

Total removal of the tumor and complete pain relief (Barrow Neurological Institute I) were achieved in all 15 patients without significant morbidity. Five patients developed new facial numbness postoperatively, which disappeared within three months after surgery. The postoperative magnetic resonance imaging showed temporal lobe swelling in three patients, but no clinical symptoms. One patient had cerebrospinal fluid leakage and was managed with bed rest and temporary lumbar drainage. One patient had an intracranial infection and was treated with antibiotics. By the last follow up, no patients had pain relapse or/and tumor recurrence. It is worth noting that the vascular compression at the root of the trigeminal nerve was found in one patient during the operation.

Conclusion

Our experience suggests that drilling off the PA and opening the upper wall of the MC are key elements for a good outcome of the treatment of TN secondary to PAM. The intradural ATPA has the advantages for both tumor resection and pain relief.

Trigeminal neuralgia and other cranial pain syndromes

Spontaneous Trigeminal Neuralgia is a painful condition of the face which may require interventional treatment if medicines fail to control the pain. These include microvascular decompression (MVD) and GKNS. The former is moderately more effective but GKNS has become accepted both as an alternative to MVD or as an adjunct. Like all treatments of the condition, it is successful in a majority of patients but by no means all. Repeat treatments are possible. When Trigeminal Neuralgia is secondary to other conditions the response to GKNS is different. With AVMs, Dural Arteriovenous Fistulae and Epidermoids, the dose to treat the visible lesion usually cures the neuralgia. With meningiomas it is necessary to treat the neuralgia as a separate entity with a neuralgia dose focused on the nerve. GKNS does not improve the rare neuralgia associated with Vestibular Schwannomas. It works with Multiple Sclerosis but not as well as with the spontaneous illness. There is some evidence that GKNS can be useful with the rare Glossopharyngeal and Sphenopalatine Neuralgias.

Historical aspects of the problem of treatment of trigeminal neuralgia and the role of neurosurgical methods in its solution (literature review)

The trigeminal nerve is a mixed fifth cranial nerve, consisting of motor and sensory components. The sensitive component receives somesthetic information from the skin and mucous membranes of the face into the central nervous system, and the motor component is responsible for the innervation of chewing muscles. One of the manifestations of the pathology of the trigeminal nerve is pain syndrome. Trigeminal neuralgia occupies the main place among neurogenic pain syndrome in the face, is characterized by а severe course and the absence of sufficiently effective methods of treatment. According to the World Health Organization (WHO), the prevalence of trigeminal neuralgia in different countries is 2–5 cases per 100 thousand people per year. Trigeminal neuralgia is classified into 3 etiologic categories. Idiopathic trigeminal neuralgia occurs without apparent cause. Classical trigeminal neuralgia is caused by vascular compression of the trigeminal nerve root. Secondary trigeminal neuralgia is the consequence of a major neurologic disease, e. g., a tumor of the cеrеbеllоpоntine angle or multiple sclerosis. Today, there are many different options for the surgical treatment of trigeminal neuralgia. microvascular decompression of the root, radiosurgical destruction of the Gasser’s node, radiofrequency destruction, glycerol rhizotomy, balloon microcompression are considered the main effective and proven surgical methods for treating trigeminal neuralgia. But the questions of diagnosing the cause of the disease and choosing an adequate surgical method for treating therapeutically resistant trigeminal neuralgia for a particular patient remain open. The development of surgical methods begins from ancient times to the present day. The main stages in the development of neurosurgical treatment methods are presented. The following surgical techniques are described: open method – microvascular decompression, and closed percutaneous destructive methods – radiofrequency destruction, glycerol rhizotomy, balloon compression, radiosurgery, cryodestruction, laser destruction, botulinum toxin injections.

Comparison of Microvascular Decompression and Two Isocenters Gamma Knife for the Treatment of Trigeminal Neuralgia Caused by Vertebrobasilar Dolichoectasia

Background: Vertebrobasilar dolichoectasia (VBD) is one of the rare causes of trigeminal neuralgia (TN). The common surgical treatments for patients with TN caused by VBD (VBD-TN) are microvascular decompression (MVD) and Gamma Knife radiosurgery (GKRS). However, the therapeutic effects of the two methods have not been clinically compared, so this study was performed to evaluate the treatment outcomes of MVD and GKRS for patients with VBD-TN.

Methods: The retrospective study was performed from March 2011 to March 2019 in Wuhan Union Hospital. A total of 80 patients diagnosed with VBD-TN were included in this study, and they were divided into the MVD group (n = 46) and GKRS group (n = 34) according to the surgical methods. The imaging data, intraoperative findings, treatment outcomes, and complications of the two groups were analyzed and compared. Meanwhile, the influencing factors of the treatment effect are also explored on the two groups.

Results: Patients who underwent MVD were younger than patients who underwent GKRS (median ages were 61.1 and 65.4 years old, respectively, p = 0.03). The median follow-up was 61.1 months for the MVD group and 56.8 months for the GKRS group. The favorable outcomes [Barrow Neurological Institute (BNI) pain score, BNI scores I–II] occurred in 97.8% of patients treated with MVD and in 78.9% of patients treated with GKRS (p = 0.009). The favorable outcomes in the percentage of patients after MVD 1, 3, 5, and 7 years were 95.7, 85.1, 74.2, and 74.2%, respectively, whereas the corresponding percentages after GKRS were 76.5, 66.2, 56.6, and 47.2%, respectively (p = 0.031). The postoperative complications (except facial numbness) in the MVD group were higher than those in the GKRS group (p = 0.036), but the incidence of new and worsening facial numbness was lower in the GKRS group (p < 0.001).

Conclusions: MVD is superior to GKRS in obtaining and maintaining favorable outcomes for patients with VBD-TN, but it also comes with more complications other than facial numbness. Thus, the treatment program can be tailored to a patient's unique condition and wishes.

Role of Gamma Knife radiosurgery in trigeminal neuralgia - Its long term outcome and prediction using Artificial neural Network model

PURPOSE

We aimed to study the long-term efficacy, prognostic factors and complications associated with the GKRS for trigeminal neuralgia.

METHODS AND MATERIALS

Prospectively created database was analyzed for these patients. We created an Artificial neural Network - using Multilayer perceptron model in SPSS 23 by including all variables whose p value were<0.5 in univariate analysis.

RESULTS

A total of 36 patients were included in the study. Patients pain free at 6 months were 25(69.44%), which reduced to 6(40 %) at 6 years. Median time to pain relief was 18.5 days. Only 5(13.88%) of them developed new onset or worsened numbness post Gamma Knife radio surgery. Median radiation dose was 80 Gy (prescribed at 100 percent isodose line). 1st GKT (P value < 0.05) and post GKT numbness (P value < 0.05) were the only factors favouring good outcome. Prior history of MVD was associated with poor pain relief post GKRS although p value was not significant (p = 0.136). ANN model could predict with 90.0 percent accuracy the favourable or unfavourable response on 11 Tested cases. In ANN model, a greater number of Pre GKT medications, previous MVD history, V2 dermatome involvement and negative history of post GKT numbness were negative prognostic factors.

CONCLUSIONS

Lesser number of pre GKRS drugs used, involvement of V1 dermatome, post GKT numbness are favourable prognostic factors. Also, history of failed MVD for trigeminal neuralgia is associated with poor outcome. Repeat GKRS failed to show improvement in BNI grades.

Long-term pain outcomes in elderly patients with trigeminal neuralgia: comparison of first-time microvascular decompression and stereotactic radiosurgery

OBJECTIVE

Common surgical treatments for trigeminal neuralgia (TN) include microvascular decompression (MVD) and stereotactic radiosurgery (SRS). The use of MVD in elderly patients has been described but has yet to be prospectively compared to SRS, which is well-tolerated and noninvasive. The authors aimed to directly compare long-term pain control and adverse event rates for first-time surgical treatments for idiopathic TN in the elderly.

METHODS

A prospectively collected database was reviewed for TN patients who had undergone treatment between 1997 and 2017 at a single institution. Standardized collection of preoperative demographics, surgical procedure, and postoperative outcomes was performed. Data analysis was limited to patients over the age of 65 years who had undergone a first-time procedure for the treatment of idiopathic TN with at least 1 year of follow-up.

RESULTS

One hundred ninety-three patients meeting the study inclusion criteria underwent surgical procedures for TN during the study period (54 MVD, 24 MVD+Rhiz, 115 SRS). In patients in whom an artery was not compressing the trigeminal nerve during MVD, a partial sensory rhizotomy (MVD+Rhiz) was performed. Patients in the SRS cohort were older than those in the MVD and MVD+Rhiz cohorts (mean ± SD, 79.2 ± 7.8 vs 72.9 ± 5.7 and 70.9 ± 4.8 years, respectively; p < 0.0001) and had a higher mean Charlson Comorbidity Index (3.8 ± 1.1 vs 3.0 ± 0.9 and 2.9 ± 1.0, respectively; p < 0.0001). Immediate or short-term postoperative pain-free rates (Barrow Neurological Institute [BNI] pain intensity score I) were 98.1% for MVD, 95.8% for MVD+Rhiz, and 78.3% for SRS (p = 0.0008). At the last follow-up, 72.2% of MVD patients had a favorable outcome (BNI score I-IIIa) compared to 54.2% and 49.6% of MVD+Rhiz and SRS patients, respectively (p = 0.02). In total, 0 (0%) SRS, 5 (9.3%) MVD, and 1 (4.2%) MVD+Rhiz patients developed any adverse event. Multivariate Cox proportional hazards analysis demonstrated that procedure type (p = 0.001) and postprocedure sensory change (p = 0.003) were statistically significantly associated with pain control.

CONCLUSIONS

In this study cohort, patients who had undergone MVD had a statistically significantly longer duration of pain freedom than those who had undergone MVD+Rhiz or SRS as their first procedure. Fewer adverse events were seen after SRS, though the MVD-associated complication rate was comparable to published rates in younger patients. Overall, the results suggest that both MVD and SRS are effective options for the elderly, despite their advanced age. Treatment choice can be tailored to a patient's unique condition and wishes.

Update on Trigeminal Neuralgia

PURPOSE OF REVIEW

To review current treatments for trigeminal neuralgia, with an emphasis on determining which patients may benefit from neurosurgical procedures.

RECENT FINDINGS

A detailed history is the most helpful tool for diagnosing trigeminal neuralgia (TN) and predicting response to neurosurgical treatments. Patients with classic trigeminal neuralgia will describe severe, unilateral, intermittent facial pain that is triggered by innocuous sensory stimuli. In most cases, pain is caused by compression of the trigeminal nerve by a blood vessel near the brainstem. Magnetic resonance imaging is necessary to rule out TN secondary to multiple sclerosis or tumor. Modern high-resolution T2 images may demonstrate neurovascular contact, particularly when analyzed by a neurosurgeon with expertise in TN. Initial management involves a trial of medication, usually carbamazepine or oxcarbazepine. Microvascular decompression (MVD) is safe and effective surgery, for patients with classic TN related to neurovascular compression. For patients with TN secondary to multiple sclerosis, and for patients who are otherwise poor candidates for MVD, neurosurgical options include percutaneous trigeminal rhizotomy and radiosurgery. Neurosurgical procedures are less effective in relieving atypical facial pain. In the clinical evaluation of a patient with facial pain, it is important to distinguish classic trigeminal neuralgia from atypical facial pain. A patient with classic trigeminal neuralgia would benefit from neurosurgical consultation. The advent of high-resolution MRI and MRA sequences now allows a neurosurgeon to detect when neurovascular compression is likely, and select the optimal procedure for treatment.

Application of an artificial neural network model for early outcome prediction of gamma knife radiosurgery in patients with trigeminal neuralgia and determining the relative importance of risk factors

OBJECTIVES

Stereotactic radiosurgery (SRS) is a minimally invasive modality for the treatment of trigeminal neuralgia (TN). Outcome prediction of this modality is very important for proper case selection. The aim of this study was to create artificial neural networks (ANN) to predict the clinical outcomes after gamma knife radiosurgery (GKRS) in patients with TN, based on preoperative clinical factors.

PATIENTS AND METHODS

We used the clinical findings of 155 patients who were underwent GKRS (from March 2000 to march 2015) at Iran Gamma Knife center, Teheran, Iran. Univariate analysis was performed for a long list of risk factors, and those with P-Value < 0.2 were used to create back-propagation ANN models to predict pain reduction and hypoesthesia after GKRS. Pain reduction was defined as BNI score 3a or lower and hypoesthesia was defined as BNI score 3 or 4.

RESULTS

Typical trigeminal neuralgia (TTN) (P-Value = 0.018) and age>65 (P-Value = 0.040) were significantly associated with successful pain reduction and three other variables including radiation dosage >85 (P-Value = 0.098), negative history of diabetes mellitus (P-Value = 0.133) and depression (P-Value = 0.190). On the other hand, radio dosage>85 (P-Value = 0.008) was significantly associated with hypoesthesia, other related risk factors (with p-Value<0.2), were history of multiple sclerosis (P-Value = 0.106), pain duration more than 10 years before GKRS (P-Value = 0.115), history of depression (P-Value = 0.139), history of percutaneous ablative procedures (P-Value = 0.148) and history of diabetes mellitus (P-Value = 0.169).ANN models could predict pain reduction and hypoesthesia with the accuracy of 84.5% and 91.5% respectively. By mutual elimination of each factor in this model we could also evaluate the contribution of each factor in the predictive performance of ANN.

CONCLUSIONS

The findings show that artificial neural networks can predict post operative outcomes in patients who underwent GKRS with a high level of accuracy. Also the contribution of each factor in the prediction of outcomes can be determined using the trained network.

Stereotactic radiosurgery for trigeminal neuralgia: a systematic review

OBJECTIVES

The aims of this systematic review are to provide an objective summary of the published literature specific to the treatment of classical trigeminal neuralgia with stereotactic radiosurgery (RS) and to develop consensus guideline recommendations for the use of RS, as endorsed by the International Society of Stereotactic Radiosurgery (ISRS).

METHODS

The authors performed a systematic review of the English-language literature from 1951 up to December 2015 using the Embase, PubMed, and MEDLINE databases. The following MeSH terms were used in a title and abstract screening: "radiosurgery" AND "trigeminal." Of the 585 initial results obtained, the authors performed a full text screening of 185 studies and ultimately found 65 eligible studies. Guideline recommendations were based on level of evidence and level of consensus, the latter predefined as at least 85% agreement among the ISRS guideline committee members.

RESULTS

The results for 65 studies (6461 patients) are reported: 45 Gamma Knife RS (GKS) studies (5687 patients [88%]), 11 linear accelerator (LINAC) RS studies (511 patients [8%]), and 9 CyberKnife RS (CKR) studies (263 patients [4%]). With the exception of one prospective study, all studies were retrospective.The mean maximal doses were 71.1-90.1 Gy (prescribed at the 100% isodose line) for GKS, 83.3 Gy for LINAC, and 64.3-80.5 Gy for CKR (the latter two prescribed at the 80% or 90% isodose lines, respectively). The ranges of maximal doses were as follows: 60-97 Gy for GKS, 50-90 Gy for LINAC, and 66-90 Gy for CKR.Actuarial initial freedom from pain (FFP) without medication ranged from 28.6% to 100% (mean 53.1%, median 52.1%) for GKS, from 17.3% to 76% (mean 49.3%, median 43.2%) for LINAC, and from 40% to 72% (mean 56.3%, median 58%) for CKR. Specific to hypesthesia, the crude rates (all Barrow Neurological Institute Pain Intensity Scale scores included) ranged from 0% to 68.8% (mean 21.7%, median 19%) for GKS, from 11.4% to 49.7% (mean 27.6%, median 28.5%) for LINAC, and from 11.8% to 51.2% (mean 29.1%, median 18.7%) for CKR. Other complications included dysesthesias, paresthesias, dry eye, deafferentation pain, and keratitis. Hypesthesia and paresthesia occurred as complications only when the anterior retrogasserian portion of the trigeminal nerve was targeted, whereas the other listed complications occurred when the root entry zone was targeted. Recurrence rates ranged from 0% to 52.2% (mean 24.6%, median 23%) for GKS, from 19% to 63% (mean 32.2%, median 29%) for LINAC, and from 15.8% to 33% (mean 25.8%, median 27.2%) for CKR. Two GKS series reported 30% and 45.3% of patients who were pain free without medication at 10 years.

CONCLUSIONS

The literature is limited in its level of evidence, with only one comparative randomized trial (1 vs 2 isocenters) reported to date. At present, one can conclude that RS is a safe and effective therapy for drug-resistant trigeminal neuralgia. A number of consensus statements have been made and endorsed by the ISRS.

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

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.

Familial Trigeminal Neuralgia Treated with Stereotactic Radiosurgery: A Case Report and Literature Review

Background

Trigeminal neuralgia (TN) is a chronic pain condition characterized by brief episodes of lancinating pain in one or more distributions of the trigeminal nerve. Episodes of pain secondary to TN are triggered by certain stimuli, such as chewing, shaving, or touching the face. Although a common cause of TN is compression of the trigeminal nerve root entry zone by an artery or vein, many cases of TN are idiopathic. However, there have been limited reports in the literature of familial TN.

Case Presentation

A 31-year-old male presented with classic TN symptoms in the right V1/V2 distribution that recently progressed to the V3 distribution a case of familial TN. His father an brother both have TN. Carbamazepine, oxcarbazepine, and rhizotomy did not improve his symptoms. He was treated with stereotactic radiosurgery (SRS) with a dose of 85 Gy delivered to the proximal trigeminal root with improvement in his pain. We also review and summarize the over 160 cases of familial TN found in the literature.

Conclusions

This is the first reported case of familial TN treated with SRS. Patients with familial TN are more likely to have bilateral disease, to present with earlier onset, and to become refractory to medical therapy and may require more aggressive approaches. We propose that SRS is a good treatment approach for these patients.

Higher dose rate Gamma Knife radiosurgery may provide earlier and longer-lasting pain relief for patients with trigeminal neuralgia

OBJECT

Gamma Knife radiosurgery (GKRS) utilizes cobalt-60 as its radiation source, and thus dose rate varies as the fixed source decays over its half-life of approximately 5.26 years. This natural decay results in increasing treatment times when delivering the same cumulative dose. It is also possible, however, that the biological effective dose may change based on this dose rate even if the total dose is kept constant. Because patients are generally treated in a uniform manner, radiosurgery for trigeminal neuralgia (TN) represents a clinical model whereby biological efficacy can be tested. The authors hypothesized that higher dose rates would result in earlier and more complete pain relief but only if measured with a sensitive pain assessment tool.

METHODS

One hundred thirty-three patients were treated with the Gamma Knife Model 4C unit at a single center by a single neurosurgeon during a single cobalt life cycle from January 2006 to May 2012. All patients were treated with 80 Gy with a single 4-mm isocenter without blocking. Using an output factor of 0.87, dose rates ranged from 1.28 to 2.95 Gy/min. The Brief Pain Inventory (BPI)-Facial was administered before the procedure and at the first follow-up office visit 1 month from the procedure (mean 1.3 months). Phone calls were made to evaluate patients after their procedures as part of a retrospective study. Univariate and multivariate linear regression was performed on several independent variables, including sex, age in deciles, diagnosis, follow-up duration, prior surgery, and dose rate.

RESULTS

In the short-term analysis (mean 1.3 months), patients’ self-reported pain intensity at its worst was significantly correlated with dose rate on multivariate analysis (p = 0.028). Similarly, patients’ self-reported interference with activities of daily living was closely correlated with dose rate on multivariate analysis (p = 0.067). A 1 Gy/min decrease in dose rate resulted in a 17% decrease in pain intensity at its worst and a 22% decrease in pain interference with activities of daily living. In longer-term follow-up (mean 1.9 years), GKRS with higher dose rates (> 2.0 Gy/min; p = 0.007) and older age in deciles (p = 0.012) were associated with a lower likelihood of recurrence of pain.

DISCUSSION

Prior studies investigating the role of dose rate in Gamma Knife radiosurgical ablation for TN have not used validated outcome tools to measure pain preoperatively. Consequently, differences in pain outcomes have been difficult to measure. By administering pain scales both preoperatively as well as postoperatively, the authors have identified statistically significant differences in pain intensity and pain interference with activities of daily living when comparing higher versus lower dose rates. Radiosurgery with a higher dose rate results in more pain relief at the early follow-up evaluation, and it may result in a lower recurrence rate at later follow-up.

Trigeminal Neuralgia and Radiofrequency Lesioning

Trigeminal Neuralgia is a disorder that is characterized with electrical-type shocking pain in the face and jaw. This pain may either present as sharp unbearable pain unilateral or bilaterally. There is no definite etiology for this condition. There are various treatment methods that are currently being used to relieve the pain. One of the pharmacological treatments is Carbamazepine and the most prevalent surgical treatments include Gamma Knife Surgery (GKS), Microvascular Decompression (MVD) and Radiofrequency Lesioning (RFL). Although, MVD is the most used surgical method it is not an option for all the patients due to the intensity of the procedure. RFL is used when MVD is not suitable. In this paper we present the various treatments and Monte-Carlo based pharmacokinetic simulations of Carbamazepine in treatment of Trigeminal Neuralgia.