Gamma knife radiosurgery on the trigeminal ganglion for idiopathic trigeminal neuralgia: Results and review of the literature

Trigeminal neuralgia

Trigeminal neuralgia (TN) is a facial pain disorder characterized by intense and paroxysmal pain that profoundly affects quality of life and presents complex challenges in diagnosis and treatment. TN can be categorized as classical, secondary and idiopathic. Epidemiological studies show variable incidence rates and an increased prevalence in women and in the elderly, with familial cases suggesting genetic factors. The pathophysiology of TN is multifactorial and involves genetic predisposition, anatomical changes, and neurophysiological factors, leading to hyperexcitable neuronal states, central sensitization and widespread neural plasticity changes. Neurovascular compression of the trigeminal root, which undergoes major morphological changes, and focal demyelination of primary trigeminal afferents are key aetiological factors in TN. Structural and functional brain imaging studies in patients with TN demonstrated abnormalities in brain regions responsible for pain modulation and emotional processing of pain. Treatment of TN involves a multifaceted approach that considers patient-specific factors, including the type of TN, with initial pharmacotherapy followed by surgical options if necessary. First-line pharmacological treatments include carbamazepine and oxcarbazepine. Surgical interventions, including microvascular decompression and percutaneous neuroablative procedures, can be considered at an early stage if pharmacotherapy is not sufficient for pain control or has intolerable adverse effects or contraindications.

Effect of lidocaine on expression of P2X7, p-p38 and IL-Iβ in the thalamus of rats with trigeminal neuralgia

We investigated whether lidocaine can increase the pain threshold of rats with trigeminal neuralgia by affecting the expression of P2X7, p-p38 and IL-Iβ proteins in the thalamus. Thirty-three male Sprague-Dawley (SD) rats were randomly divided into three groups (n = 11): Sham group, Ion-CCI (infraorbital nerve chronic constriction injury) group and Ion-CCI+L group(Ion-CCI+lidocaine 10 mg/kg/day, i.p.). The mechanical pain threshold of rats was measured preoperatively and at 1, 3, 5, 7, 9, 11 and 14days after operation with the von Frey filament sensor tester. Fourteen days after operation, the rats were dissected to collect their whole brain, thalamus and trigeminal ganglion to detect IL-1β, P2X7, p38, and p-p38 protein expression. The pain threshold of rats in Ion-CCI+L group was lower than that in Sham group (p < 0.01) and higher than that in Ion-CCI group (p < 0.01).ELISA showed that IL-1β in the thalamus and trigeminal ganglion in Ion-CCI+L group were lower than those in ion-CCI group (p < 0.05) but higher than those in Sham group (p < 0.05). Western blot showed that the expression levels of P2X7 and p-p38 in the thalamus of rats in Ion-CCI+L group were lower than those in Ion-CCI group (p < 0.01) and higher than thaose in Sham group (p < 0.01),while the expression levels of IL-1β in the thalamus in Ion-CCI+L group were lower than those in Ion-CCI group (p < 0.05) and higher than those in Sham group (p < 0.01). Immunofluorescence showed that p-p38 in the thalamus in Ion-CCI+L group was lower than that in Ion-CCI group (p < 0.05) and higher than that in Sham group (p < 0.05). Lidocaine can reduce the inflammatory response of the central nervous system and increase the pain threshold of trigeminal neuralgia rats by inhibiting p2x7-p38-IL-1β signaling pathway.This pathway play an important role in the pathogenesis of trigeminal neuralgia, and it may be one of the targets for the treatment of trigeminal neuralgia.

Trigeminal ganglion itself can be a viable target to manage trigeminal neuralgia

Excruciating trigeminal neuralgia (TN) management is very difficult and severely affects the patient's quality of life. Earlier studies have shown that the trigeminal ganglion (TG) comprises several receptors and signal molecules that are involved in the process of peripheral sensitization, which influences the development and persistence of neuropathic pain. Targeting TG can modulate this sensitization pathway and mediate the pain-relieving effect. So far,there are few studies in which modulation approaches to TG itself have been suggested so far. "Trigeminal ganglion modulation" and "trigeminal neuralgia" were used as search phrases in the Scopus Index and PubMed databases to discover articles that were pertinent to the topic. In this review, we address the role of the trigeminal ganglion in TN and underlying molecules and neuropeptides implicated in trigeminal pain pathways in processing pathological orofacial pain. We also reviewed different modulation approaches in TG for TN management. Furthermore, we discuss the prospect of targeting trigeminal ganglion to manage such intractable pain.

Microvascular decompression as a second step treatment for trigeminal neuralgia in patients with failed two-isocentre gamma knife radiosurgery

OBJECTIVE

Subsequent microvascular decompression (MVD) might be affected by the previous two-isocentre gamma knife radiosurgery (GKS) due to the tissue changes caused by its higher dose radiation and larger treatment volume. This study aimed to evaluate the safety and efficacy of MVD as a second step treatment after two-isocentre GKS.

METHODS

Between December 2016 and May 2019, data from 19 consecutive trigeminal neuralgia (TN) patients who experienced MVD after failed two-isocentre GKS were collected. The clinical characteristics, intraoperative findings, surgical outcomes and complications were reviewed and compared with 158 patients who underwent MVD as an initial treatment.

RESULTS

Fifteen patients (78.9%) achieved complete pain relief (Barrow Neurological Institute, BNI class I) immediately after surgery and nine patients (47.4%) maintained complete pain relief at the last follow-up, which was similar to patients who underwent initial MVD. The median follow-up period was 36 months. The incidence of new or worsened facial numbness showed no statistical significance between the groups. During surgery, trigeminal nerve atrophy was noted in 9 patients (47.4%), thickened arachnoid in 3 patients (15.8%), atherosclerotic plaque in 3 patients (15.8%) and neurovascular adhesion in 1 patient (5.3%).

CONCLUSIONS

MVD remains an effective and safe rescue therapy for patients who elect the minimally invasive treatment with two-isocentre GKS for the first time, without an increased risk of facial numbness.

Cranial Neuralgias

PURPOSE OF REVIEW

This article discusses the differential diagnosis, evaluation, and management of trigeminal neuralgia and reviews other neuralgias of the head and neck, including those that contribute to neuralgic ear pain.

RECENT FINDINGS

Most cases of trigeminal neuralgia are related to vascular compression, a demyelinating plaque, or a compressive mass affecting the trigeminal nerve. However, recent studies have shown that up to 11% of patients have a family history of trigeminal neuralgia, suggesting that some patients may have a genetic predisposition to demyelination or nerve hyperexcitability. In these patients, trigeminal neuralgia may occur at a younger age, on both sides of the face, or in combination with other neuralgias.

SUMMARY

When a patient presents with neuralgic pain, the diagnosis is made by careful history and neurologic examination, with attention to the dermatome involved, the triggers, and the presence of any associated sensory deficit. All patients with new neuralgia or neuropathic facial pain warrant a careful evaluation for a secondary cause. The presence of sensory deficit on bedside examination is particularly concerning for an underlying secondary etiology.

Radionecrosis and cellular changes in small volume stereotactic brain radiosurgery in a porcine model

Stereotactic radiosurgery (SRS) has proven an effective tool for the treatment of brain tumors, arteriovenous malformation, and functional conditions. However, radiation-induced therapeutic effect in viable cells in functional SRS is also suggested. Evaluation of the proposed modulatory effect of irradiation on neuronal activity without causing cellular death requires the knowledge of radiation dose tolerance at very small tissue volume. Therefore, we aimed to establish a porcine model to study the effects of ultra-high radiosurgical doses in small volumes of the brain. Five minipigs received focal stereotactic radiosurgery with single large doses of 40–100 Gy to 5–7.5 mm fields in the left primary motor cortex and the right subcortical white matter, and one animal remained as unirradiated control. The animals were followed-up with serial MRI, PET scans, and histology 6 months post-radiation. We observed a dose-dependent relation of the histological and MRI changes at 6 months post-radiation. The necrotic lesions were seen in the grey matter at 100 Gy and in white matter at 60 Gy. Furthermore, small volume radiosurgery at different dose levels induced vascular, as well as neuronal cell changes and glial cell remodeling.