Retrogasserian trigeminal radiofrequency-thermorhizotmoy for trigeminal neuralgia.

Based on a personal experience of 4200 surgeries, radiofrequency thermocoagulation is useful lesional treatment for those trigeminal neuralgias (TNs) not amenable to microvascular decompression (idiopathic or secondary TNs). Introduced through the foramen ovale, behind the trigemnial ganglion in the triangular plexus, the needle is navigated by radiology and neurophysiological testing to target the retrogasserian fibers corresponding to the trigger zone. Heating to 55-75 °C can achieve hypoesthesia without anaesthesia dolorosa if properly controlled. Depth of anaesthesia varies dynamically sedation for cannulation and lesioning, and awareness during neurophysiologic navigation. Proper technique ensures long-lasting results in more than 75% of patients.

Neurophysiological mechanisms of hypertonia and hypotonia in children with spastic cerebral palsy: surgical implications.

Mechanism of hypertonia in cerebral palsy children is dual: a neural component due to spasticity (velocity dependent) and a biomechanical component linked to soft tissue changes. Their differentiation-which might be clinically difficult-is however crucial, as only the first component will respond to anti-spastic treatments, the second to physiotherapy. Furthermore, spasticity is frequently associated with dystonia, which is a sustained hypertonic state induced by attempts at voluntary motion. Spasticity and dystonia have to be carefully distinguished as dorsal rhizotomy will not significantly influence the dystonic component. Spasticity, which by definition opposes to muscle stretching and lengthening, has two important consequences. First, the muscles tend to remain in a shortened position, which in turn results in soft tissue changes and contracture. The second is that movements are restricted. Thus, both hypertonia and lack of mobilization create a vicious circle leading to severe locomotor disability linked to irreducible musculotendinous retraction and joint ankylosis/bone deformities. These evolving consequences should be highly considered during the child's assessment for decision-making. The hypotonic effects of lumbosacral dorsal rhizotomy, which are not only segmental on the lower limbs but also supra-segmental through the reticular formation, are finally discussed.

Percutaneous biopsy through the foramen ovale for parasellar lesions: surgical anatomy, method, and indications.

Knowledge of the pathological diagnosis before deciding the best strategy for treating parasellar lesions is of prime importance, due to the relative high morbidity and side-effects of open direct approaches to this region, known to be rich in important vasculo-nervous structures. When imaging is not evocative enough to ascertain an accurate pathological diagnosis, a percutaneous biopsy through the transjugal-transoval route (of Hartel) may be performed to guide the therapeutic decision.The chapter is based on the authors' experience in 50 patients who underwent the procedure over the ten past years. There was no mortality and only little (mostly transient) morbidity. Pathological diagnosis accuracy of the method revealed good, with a sensitivity of 0.83 and a specificity of 1.In the chapter the authors first recall the surgical anatomy background from personal laboratory dissections. They then describe the technical procedure, as well as the tissue harvesting method. Finally they define indications together with the decision-making process.Due to the constraint trajectory of the biopsy needle inserted through the Foramen Ovale, accessible lesions are only those located in the Meckel trigeminal Cave, the posterior sector of the cavernous sinus compartment, and the upper part of the petroclival region.The authors advise to perform this percutaneous biopsy method when imaging does not provide sufficient evidence of the pathological nature of the lesion, for therapeutic decision. Goal is to avoid unnecessary open surgery or radiosurgery, also inappropriate chemo-/radio-therapy.

Dorsal rhizotomy in cerebral palsy: How root sectioning is influenced by intraoperative neuromonitoring?

INTRODUCTION AND OBJECTIVE: Dorsal rhizotomy is a controversial procedure for treating spasticity in children with cerebral palsy, particularly regarding the influence of intraoperative neuromonitoring (ION). The objective of this study was to evaluate the influence of ION in adjusting root sectioning compared the preoperative program established by the multidisciplinary team. MATERIAL AND METHODS: Twenty-four consecutive children with spastic diplegia or quadriplegia, operated on between 2017 and 2020 in the University Hospital of Nancy, France, were studied. All underwent the same procedure: Keyhole Intralaminar Dorsal rhizotomy (KIDr) with enlarged multilevel interlaminar openings to access all roots from L2 to S2. The Ventral Root (VR) was stimulated to map radicular myotomes, and the Dorsal Root (DR) to test excitability of the segmental circuitry. Muscle responses were observed independently by the physiotherapist and by EMG-recordings. The study compared final root sectioning per radicular level and per side after ION versus the preoperative program determined by the multidisciplinary team. RESULTS: ION resulted in significant differences in final percentage root sectioning (P<0.05), with a decrease for L2 and L3 and an increase for L5. ION modified the symmetry of sectioning, with 32% instead of 5% in preoperative program. Only 5 children showed change in GMFC score 6 months after surgery. CONCLUSION: The use of ION during dorsal rhizotomy led to important modifications of root sectioning during surgery, which justifies individual control of each root, level by level and side by side, to optimize the therapeutic effect.

Functional exploration for neuropathic pain.

Neuropathic pain (NP) may become refractory to conservative medical management, necessitating neurosurgical procedures in carefully selected cases. In this context, the functional neurosurgeon must have suitable knowledge of the disease he or she intends to treat, especially its pathophysiology. This latter factor has been studied thanks to advances in the functional exploration of NP, which will be detailed in this review. The study of the flexion reflex is a useful tool for clinical and pharmacological pain assessment and for exploring the mechanisms of pain at multiple levels. The main use of evoked potentials is to confirm clinical, or detect subclinical, dysfunction in peripheral and central somato-sensory pain pathways. LEP and SEP techniques are especially useful when used in combination, allowing the exploration of both pain and somato-sensory pathways. PET scans and fMRI documented rCBF increases to noxious stimuli. In patients with chronic NP, a decreased resting rCBF is observed in the contralateral thalamus, which may be reversed using analgesic procedures. Abnormal pain evoked by innocuous stimuli (allodynia) has been associated with amplification of the thalamic, insular and SII responses, concomitant to a paradoxical CBF decrease in ACC. Multiple PET studies showed that endogenous opioid secretion is very likely to occur as a reaction to pain. In addition, brain opioid receptors (OR) remain relatively untouched in peripheral NP, while a loss of ORs is most likely to occur in central NP, within the medial nociceptive pathways. PET receptor studies have also proved that antalgic Motor Cortex Stimulation (MCS), indicated in severe refractory NP, induces endogenous opioid secretion in key areas of the endogenous opioid system, which may explain one of the mechanisms of action of this procedure, since the secretion is proportional to the analgesic effect.

SEEG-guided RF-thermocoagulation of epileptic foci: a therapeutic alternative for drug-resistant non-operable partial epilepsies.

BACKGROUND: Previous literature includes numerous reports of acute stereotactic ablation for epilepsy. Most reports focus on amygdalotomies or amygdalohippocampotomies, some others focus on various extra-limbic targets. These stereotactic techniques proved to have a less favourable outcome than that of standard surgery, so that their rather disappointing benefit/risk ratio explains why they have been largely abandoned. However, depth electrode recordings may be required in some cases of epilepsy surgery to delineate the best region of cortical resection. We usually implant depth electrodes according to Talairach's stereo electroencephalography (SEEG) methodology. Using these chronically implanted depth electrodes, we are able to perform radiofrequency (RF)-thermolesions of the epileptic foci. This paper reports the technical data required to perform such multiple cortical thermolesions, as well as the results in terms of seizure outcome in a group of 41 patients. TECHNICAL DATA: Lesions are placed in the cortex areas showing either a low amplitude fast pattern or spike-wave discharges at the onset of the seizures. Interictal paroxysmal activities are not considered for planning thermocoagulation sites. All targets are first functionally evaluated using electrical stimulation. Only those showing no clinical response to stimulation are selected for thermolesion, including sites located inside or near primary functional area. Lesions are performed using 120mA bipolar current (50 V), applied for 10-30 sec. Each thermocoagulation produces a 5-7mm diameter cortical lesion. A total of 2-31 lesions were performed in each of the 41 patients. Lesions are placed without anaesthesia. RESULTS: 20 patients (48.7%) experienced a seizure frequency decrease of at least 50% that was more than 80% in eight of them. One patient was seizure free after RF thermocoagulation. In 21 patients, no significant reduction of the seizure frequency was observed. Amongst the characteristics of the disease (age and sex of the patient, lobar localization of the EZ) and the characteristics of the thermocoagulations (topography, lateralization, number, morphology of the lesions on MRI) no factor was significantly linked to the outcome. However, the best results were clearly observed in epilepsies symptomatic of a cortical development malformation (CDM), with 67% of responders in this group of 20 patients (p = 0.052). Three transient post-procedure side-effects, consisting of paraesthetic sensations in the mouth (2 cases), and mild apraxia of the hand, were observed. CONCLUSION: SEEG-guided-RF-thermolesioning is a safe technique. Our results indicate that such lesions can lead to a significant reduction of seizure frequency. Our experience suggests that SEEG-guided RF thermocoagulation should be dedicated to drug-resistant epileptic patients for whom conventional resection surgery is risky or contra-indicated on the basis of invasive pre-surgical evaluation, particularly those suffering from epilepsy symptomatic of cortical development malformation.

Benefits and pitfalls of percutaneous biopsy for cavernous sinus tumors through the foramen ovale: two case reports.

Case 1, a 61-year-old female presented with paresthesia of her right upper lip. Computed tomography (CT) and magnetic resonance (MR) imaging with contrast material revealed an enhanced mass in the right Meckel's cave, which included the lateral and posterior parts of the cavernous sinus and surrounded the right internal carotid artery. To establish the best surgical strategy, a percutaneous biopsy through the foramen ovale was performed, and the histological examination indicated that the tumor was a transitional meningioma. We performed combined treatment with microsurgery and radiosurgery. Case 2,a 66-year-old female presented with paresthesia of the right side of her face. MR images with gadolinium revealed an abnormal enhanced mass at the right Meckel's cave, and a CT scan with a bone window showed a large foramen ovale in the right side. We performed a percutaneous biopsy using the same method, but this tumor was too hard to sample through the needle. Although this manipulation has the major advantage of establishing the best therapeutic strategy and avoiding unnecessary surgery, special care should be taken for hard tumors, especially for those aspirated by needle biopsy.

Decompression for Chiari type I-malformation (with or without syringomyelia) by extreme lateral foramen magnum opening and expansile duraplasty with arachnoid preservation: comparison with other technical modalities (Literature review).

Posterior craniocervical decompression is the procedure most currently used for treating Chiari I malformation (alone or in association with syringomyelia in the absence of hydrocephalus). We reviewed the various technical modalities reported in the literature. We present a personal series of 44 patients harboring Chiari type I malformation (CM-I) operated with a suboccipital craniectomy and a C1 (or C1/C2) laminectomy, plus an extreme lateral Foramen Magnum opening, a "Y" shaped dural incision with preservation of the arachnoid membrane, and an expansile duraplasty employing autogenous periosteum. Outcomes were analyzed with follow-up ranging from 1 to 10 years (4 years on average). The presented technique was compared with the other surgical modalities reported in the literature. This comparative study shows that this type of craniocervical decompression achieved the best results with minimal complications and side-effects. Syringomyelia associated with CM-I must be treated by craniocervical decompression alone. Shunting no longer appears to be an appropriate method of treatment for syringomyelia.

[Treatment of trigeminal neuralgia with thermorhizotomy]. / Traitement de la névralgie trigéminale par thermorhizotomie.

Percutaneous radiofrequency (RF) thermorhizotomy of the trigeminal nerve is an effective treatment for trigeminal neuralgia. Long-term efficacy is proportional to the degree of postoperative hypoesthesia. The advantage is the topographic selectivity of the thermolesion, provided the electrode tip is placed accurately. This requires precise x-ray guidance and neurophysiological testing. In addition to the indication in idiopathic trigeminal neuralgia, especially for elderly patients with precarious conditions, thermorhizotomy is particularly useful for treating patients with trigeminal neuralgia due to multiple sclerosis. It can also be applied to symptomatic neuralgias, but only when the main components are of the paroxysmal and/or the allodynic types ; the thermorhizotomy method could aggravate permanent components, especially when burning pain predominates; it could also increase preexisting trophic disturbances, particularly keratitis.

[Treatment of trigeminal neuralgia with glycerol injection at the gasserian ganglion]. / Traitement de la névralgie trigéminale par injection de glycérol au niveau du ganglion de Gasser.

Gasserian ganglion neurolysis with glycerol injected percutaneously through the foramen ovale continues to be widely used. Its long-term efficacy on pain is proportional to the degree of postoperative hypoesthesia. The advantage is low cost. The disadvantage is essentially the difficulty in controlling diffusion outside the Meckel cavity. Subsequently its effects are somewhat random and potential complications are difficult to prevent reliably.

[Neurosurgical treatment of vago-glossopharyngeal neuralgia]. / Traitement neurochirurgical de la névralgie vago-glossopharyngienne.

Glossopharyngeal neuralgia, more accurately called vago-glossopharyngeal neuralgia (VGPN) because of the frequent association with pain irradiation in the sensory territory of the vagus nerve, is not always recognized because its incidence is much lower than the incidence of trigeminal neuralgia (100 times more frequent). As in trigeminal neuralgia, when pain becomes resistant to anticonvulsants - its specific medical treatment - VGPN can almost always be cured by surgery. The first option is microvascular decompression, since vascular compression is the main cause of the neuralgia. Percutaneous thermorhizotomy at the foramen jugularis (pars nervosa) is only indicated as a second option, because of unavoidable sensorimotor deficits in the ninth and tenth nerves. Tractonucleotomies at the medullary level should be reserved essentially for pain of malignant origin.

[Vascular decompression as treatment of essential arterial hypertension]. / Décompression vasculaire pour traitement de l'hypertension artérielle essentielle.

MVD of the left rostral ventrolateral medulla oblongata may be an effective treatment for patients suffering from intractable severe systemic blood hypertension. This article presents a literature review. Further clinical controlled studies have to be conducted to define precise indications.

[Algorithms for neurosurgical treatment of trigeminal neuralgia]. / Arbre décisionnel pour le traitement neurochirurgical de la névralgie du trijumeau.

Surgery should be considered only after anticonvulsant medications have failed or if medical treatment is not well-tolerated, including in cases of asthenia or drowsiness. In most reference centers, consensus is that MVD is the first option when patients are in good health. Percutaneous lesioning operations or radiosurgery are preferable in patients with adverse co-morbidity or those who are not willing to undergo open surgery.

[Neurosurgical treatment of primary hemifacial spasm with microvascular decompression]. / Traitement neurochirurgical du spasme hémifacial primaire par décompression vasculaire microchirurgicale.

In nearly all cases, primary hemifacial spasm is related to arterial compression of the facial nerve in the root exit zone at the brainstem. The offending arterial loops originate from the posterior inferior cerebellar, anterior inferior cerebellar, or vertebrobasilar artery. In as many as 40% of the patients, neurovascular conflicts are multiple. The cross-compression at the brainstem is almost always seen on magnetic resonance imaging combined with magnetic resonance angiography. Botulinum toxin can be useful by alleviating the symptoms, but the effects are inconstant and only transient. The definitive conservative treatment is microvascular decompression (MVD), which cures the disease in 85 to 95% of patients. In expert hands, the MVD procedure can be done with relatively low morbidity. Because cure of spasms is frequently delayed - by several months to even a few years -, we do not recommend early reoperation in patients with failure or until at least 1 year of follow-up. Delayed cure could well be explained by the slow reversal of the plastic changes in the facial nucleus that may have caused the symptoms.

[Clinical aspects of trigeminal neuralgia]. / Aspects cliniques de la névralgie du trijumeau.

Primary trigeminal neuralgia, termed "classical" in the international nomenclature, is an epilepsy-like disease. Diagnosis is easy when the disorder typical in presentation, based on clinical features and responsiveness to anticonvulsants. However, diagnosis can be difficult when atypical and/or in the long-duration forms. Furthermore, trigeminal neuralgia - even if typical in its clinical aspects - may be caused by a specific lesion and reveal a pathology. In other words, it may be symptomatic (secondary). Imaging, especially MRI, is of prime importance in identifying the cause and guiding the appropriate treatment.

[Predictive value of MRI for detecting and characterizing vascular compression in cranial nerve hyperactivity syndromes (trigeminal and facial nerves)]. / Valeur prédictive de l'IRM pour la détection et la caractérisation de la compression vasculaire dans les syndromes d'hyperactivité des nerfs crâniens (trijumeau et facial).

MRI detects vascular compression of the cranial nerve in the majority of the cases. High-resolution 3D-T1 and 3D-T2 MRI gives detailed images, particularly the 3D-T2 MRI sequences, with good contrast between cerebrospinal fluid and vascular and nerve structures. TOF-AMR (native sequence and vertebrobasilar reconstruction) shows the vascular structures in hypersignal and therefore differentiates the vessels from the cranial nerves. The 3D-T1 sequence with gadolinium reinforces the signal of the venous structures. Thus, preoperative MRI makes it possible to predict the existence of a vascular compression. The correlation study between imaging data and intraoperaitive anatomical findings showed a sensitivity of MRI of 97% and a specificity of 100%. In addition, it can specify the type and the degree of the compression. This information may help in selecting the most appropriate surgical method.

[Treatment of trigeminal neuralgia with microvascular decompression]. / Traitement de la névralgie trigéminale par décompression vasculaire microchirurgicale.

Pure microvascular decompression (MVD) can cure (that is, no pain, no medication) primary trigeminal neuralgia (TN) caused by vascular compression in 75% of patients (90% when compression is pronounced), according to a Kaplan-Meier survival study at 15 years. MRI with high resolution evidences neurovascular conflicts with good reliability. The results were found to be significantly better when the prosthesis implanted to maintain the compressive vessel away was not touching the nerve. This argues in favor of a real decompressive mechanism of the MVD procedure, rather than a conduction block. Because pure MVD generally does not produce hypoesthesia in the painful territory, MVD is the first surgical therapeutic option for patients with neuralgia resistant to anticonvulsive medications.

[Microsurgical anatomy of the transoval percutaneous route to the trigeminal cave and the trigeminal ganglion]. / Anatomie microchirurgicale de la voie percutanée transovale vers la cavité trigéminale et le ganglion trigéminal (voie de Hartel).

The percutaneous Hartel transoval route goes through an inverted pyramid, with an inferior summit and a superior base that includes three compartments. The danger of the inferior compartment is the parotid duct. The middle compartment contains many branches of the mandibular nerve. The superior compartment is crossed by the internal maxillary artery and its branches, as well as the auditory tube. The base of the pyramid presents not only the foramen ovale, but also the foramen lacerum, where the trocar may injure the internal carotid, and the foramen jugulare, where the trocar may meet the internal jugular vein and nerves of the pars nervosa (IX, X, XI). The trigeminal cave contains, within the trigeminal cistern, the trigeminal ganglion, extended backward by the triangular plexus (the target for thermocoagulation). These structures are undercrossed by the masticatory motor branch of the trigeminal nerve.

[Imaging anatomy of cranial nerves]. / Imagerie anatomique des nerfs crâniens.

Knowledge of the anatomy of the cranial nerves is mandatory for optimal radiological exploration and interpretation of the images in normal and pathological conditions. CT is the method of choice for the study of the skull base and its foramina. MRI explores the cranial nerves and their vascular relationships precisely. Because of their small size, it is essential to obtain images with high spatial resolution. The MRI sequences optimize contrast between nerves and surrounding structures (cerebrospinal fluid, fat, bone structures and vessels). This chapter discusses the radiological anatomy of the cranial nerves.