The nerve of McKenzie: anatomic study with application to intradural rhizotomy for spasmodic torticollis.

INTRODUCTION: Medically recalcitrant spasmodic torticollis may necessitate surgical intervention. One procedure used for this pathologic entity is intradural rhizotomy. However, some patients are symptomatic, perhaps due to an overlooked or underappreciated nerve of McKenzie. The authors' goal was to further elucidate the anatomy of this nerve of the craniocervical junction. MATERIALS AND METHODS: Fifteen adult cadavers (30 sides) underwent microsurgical dissection and observations of the nerve of McKenzie. Morphometrics were performed and anatomic relationships were documented under surgical magnification. RESULTS: The nerve of McKenzie was found on 70% of sides and was always a single branch. Average length was 5.2 mm for left sides and 6 mm for right sides. Average diameter was 0.9 mm (0.5-1.2 mm). In two specimens, the nerve was found bilaterally. It pierced the first denticulate ligament on 11 sides (52.4%) and travelled through its two prongs on three sides (14.3%) to connect to the anteriorly placed C1 ventral root. On five sides, it was in intimate contact with the adventitia of the vertebral artery. It was more common on right sides and in males, and this was statistically significant. CONCLUSIONS: The authors identified the nerve of McKenzie in most specimens. This nerve, if overlooked during surgical treatment of spasmodic torticollis, may result in continued symptoms. The nerve of McKenzie was often concealed within the denticulate ligament or adventitia of the vertebral artery. The authors hope the data presented here will aid neurosurgeons and decrease complications in patients who undergo neurotomy for spasmodic torticollis.

Intraoperative Mapping of the Sensory Root of the Trigeminal Nerve in Patients with Pontocerebellar Angle Pathology.

OBJECTIVE: The aim of the present study was to determine the position of the 3 sensory branches of the trigeminal nerve in the preganglionic tract using intraoperative neurophysiological mapping. METHODS: We included consecutive adult patients who underwent neurosurgical treatment of cerebellopontine angle lesions. The trigeminal nerve was antidromically stimulated at 3 sites along its circumference with different stimulus intensities at a distance of ≤1 cm from the brainstem. The sensory nerve action potentials (SNAPs) were recorded from each main trigeminal branch (V1 [ophthalmic branch], V2 [maxillary branch], and V3 [mandibular branch]). RESULTS: We analyzed 13 patients. The stimulation points at which we obtained the greatest number of congruous and exclusive SNAPs (SNAPs only on the stimulated branch) was the stimulation point for V3 (20.7%). The stimulation intensity at which we obtained the highest number of congruent and exclusive SNAPs with the stimulated branch was 0.5 mA. CONCLUSIONS: Using our recording conditions, trigeminal stimulation is a reliable technique for mapping the V3 and V1 branches using an intensity not exceeding 0.5. However, reliable identification of the fibers of V2 is more difficult. Stimulation of the trigeminal nerve can be a reliable technique to identify the V3 and V1 branches if rhizotomy of these branches is necessary.

Neural activity in trigeminal neuralgia patients with sensory and motor stimulations: A pilot functional MRI study.

OBJECTIVE: Trigeminal neuralgia (TN) is a neuropathic pain syndrome that typically exhibits paroxysmal pain. However, the true mechanism of pain processing is unclear. We aim to evaluate the neural activity changes, before and after radiofrequency rhizotomy, in TN patients using functional MRI (fMRI) with sensory and motor stimulations. METHODS: Six patients with classical TN participated in the study. Each patient underwent two boxcar paradigms of fMRI tasks: air-sensation and jaw-clenching around 1-3 weeks before and after the surgical intervention. McGill Pain Questionnaire (MPQ) was used to evaluate the pain intensity prior to fMRI study. RESULTS: Before rhizotomy, the jaw-clenching stimulation yielded reduced brain activation in primary motor (M1) and primary (SI) and secondary somatosensory (SII) cortices. Following intervention, activation in those regions returned to near normal levels observed in healthy subjects. For air-sensation stimulation, several pain and pain modulation regions such as right thalamus, right putamen, insula, and brainstem, were activated before the intervention, but subsided after the intervention. This correlated well with the change of MPQ scores (p < 0.01). CONCLUSIONS: In our study, we observed significant pain reduction accompanied by increased motor activities after rhizotomy in patients with TN. We hypothesize that the reduced motor activities identified in fMRI may be reversed after the treatment with radiofrequency rhizotomy. More research is warranted.

Technical communication: percutaneous radiofrequency mandibular nerve rhizotomy guided by high-speed real-time computed tomography fluoroscopy.

We present a new method of percutaneous radiofrequency mandibular nerve rhizotomy for pain relief in the mandibular region, in which needle placement is guided by high-speed real-time computed tomography (CT) fluoroscopy. Eleven patients (13 procedures) with idiopathic trigeminal neuralgia underwent the procedure. CT fluoroscopy simultaneously provided 3 slices (1-mm interval series, craniocaudally) in 1 fluoroscopic view, allowing for accurate needle placement. Trigeminal neuralgia improved in all patients without severe complications. The mean numerical rating scales of pain intensity (+ or - sd) decreased from 6.5 (+ or - 1.8, pretreatment) to 1.8 (+ or - 1.7, 1 month after treatment) and to 0.9 (+ or - 1.0, 3 months after treatment). Our limited-case series suggests potential advantages for the new CT fluoroscopy guidance, but these findings await confirmation from randomized controlled trials and large-case series.

Incidence, morphology and morphometry of the foramen of Vesalius: complementary study for a safer planning and execution of the trigeminal rhizotomy technique.

BACKGROUND: The foramen of Vesalius (FV) is located in the greater wing of the sphenoid bone between the foramen ovale (FO) and the foramen rotundum in an intracranial view. The FO allows the passage of the mandibular branch of trigeminal nerve, which is the target of the trigeminal radiofrequency rhizotomy. OBJECTIVE: We analyzed its location, morphology, morphometry and interrelation among other foramina. MATERIALS AND METHODS: 400 macerated adult human skulls were examined. A digital microscope (Dino-Lite plus) was used to capture images from the FV. A digital caliper was used to perform the measurements of the distance between the FV and other foramina (FO, foramen spinosum and the carotid canal) in an extracranial view of the skull base. RESULTS: In the 400 analyzed skulls, the FV was identified in 135 skulls (33.75%) and absent on both sides in 265 skulls (66.25%). The FV was observed present bilaterally in 15.5% of the skulls. The incidence of unilateral foramen was 18.25% of the skulls of which 7.75% on right side and 10.5% on left side. The diameter of the FV was measured and we found an average value of 0.65 mm, on right side 0.63 mm and on the left side 0.67 mm. We verified that positive correlations were statistically significant among the three analyzed distances. CONCLUSIONS: This study intends to offer specific anatomical data with morphological patterns (macroscopic and mesoscopic) to increase the understanding of the FV features as frequency, incidence and important distances among adjacent foramina.

Biplane Fluoroscopic-Guided Balloon Rhizotomy for Trigeminal Neuralgia: A Technical Note.

BACKGROUND: The classic percutaneous technique used to cannulate the foramen ovale for the treatment of trigeminal neuralgia can place important anatomic structures, such as the distal cervical internal carotid artery, at risk. OBJECTIVE: To use fixed anatomic landmarks to safely and reliably locate the foramen ovale on anteroposterior (AP) fluoroscopy. METHODS: Locating the foramen ovale was initially tested using AP fluoroscopy on cadaveric skulls in the neurosurgical simulation lab. Fluoroscopic landmarks were identified and utilized to assist in successfully locating the foramen ovale during percutaneous balloon rhizotomy procedures in patients with trigeminal neuralgia. This technique has been successfully used in multiple patients. In this report, we describe our technique in detail. RESULTS: The AP fluoroscopy is directed laterally in the coronal plane until a line drawn inferiorly from the lateral orbital rim bisects the inner concavity of the mandibular angle. Fluoroscopy is then directed inferiorly until the top of the petrous ridge bisects the mandibular ramus. The foramen ovale will come into view within the window between the mandibular ramus and hard palate. Two case illustrations are provided. CONCLUSION: Balloon rhizotomy is a commonly used treatment option for trigeminal neuralgia. Direct visualization of the foramen ovale can reliably be achieved on AP fluoroscopy using specific anatomic landmarks. This technique can be utilized to increase the accuracy and safety of the procedure.

A history of the Jannetta procedure.

Peter Jannetta was a neurosurgery resident when he proposed the neurovascular compression theory. He built upon the astute observations of Dandy, Gardner, and others who, in the era before the operating microscope, had successfully ventured into the posterior fossa. In 1965, Jannetta performed cranial nerve microdissections for dental students and identified the trigeminal portio intermedia. He proposed that preservation of these sensory fibers may avoid complete facial numbness, and together with Robert Rand developed a subtemporal transtentorial approach for selective rhizotomy for trigeminal neuralgia (TN). Such rash surgery, using an operating microscope, was then forbidden at their University of California, Los Angeles center, so they collaborated with John Alksne to perform the first surgery at Harbor General Hospital. Upon visualizing the trigeminal nerve root, Jannetta was surprised to see a pulsating superior cerebellar artery compressing the nerve and said "That's the cause of the tic." He also hypothesized that alleviating the observed vascular cross-compression may be curative.A few months later, while assessing a patient with hemifacial spasm, Jannetta had the epiphany that this was the same disease process as TN, but instead affecting the facial nerve. The patient consented to what would become Jannetta's first microvascular decompression procedure. The senior faculty members who had forbidden such surgery were away, so the supervising neurosurgeon, Paul Crandall, granted the approval to perform the surgery and assisted. Via a retromastoid approach with the patient in the sitting position and using the operating microscope, Jannetta identified and alleviated the culprit neurovascular compression, with a cure resulting.Jannetta presented his neurovascular compression theory and operative findings to the neurosurgical patriarchy of the time. Elders of the field were generally not inclined to accept the bold speculations of an untested neurosurgeon, and were often determined to discredit the new "cure" of the old diseases. Over decades of refining his surgical technique, documenting the outcomes, and enduring the skepticism he often faced, Jannetta's theory and his microvascular decompression procedure withstood critical analysis and have become recognized as one the great discoveries and advances in neurosurgery and medicine.

Angle Evaluation of Possible Routes that Can Be Used to Reach the Foramen Ovale in the Anterior Approach / Evaluación Angular de Posibles Rutas que se Pueden Utilizar para Alcanzar el Foramen Oval en el Abordaje Anterior

SUMMARY: For the treatment of trigeminal neuralgia, the foramen ovale is reached by entering the cheek with a needle. Thermocoagulation is performed with balloon compression, administration of alcohol or radiofrequency. Apart from the classical method, it is theoretically possible to reach the foramen ovale through the mouth with the anterior approach. In our study, it was aimed to examine horizontally and vertically the angular values that must be given to the needle to reach the foramen ovale in the anterior approach. Three landmark points were determined on both right and left sides of 25 dry skulls. A rod was inserted starting from these landmark points and passing through the center of the foramen ovale. The vertical and horizontal angular values of this bar were measured. For each foramen ovale, 3 vertical angles, 3 horizontal angles and 4 distance measurements were made. There was a significant difference between the right and left sides in terms of horizontal angular values. Average values of horizontal angles (in degrees); on the right, 7.29 for H1, 12.15 for H2, 32.29 for H3; 1.26 for H1, 9.46 for H2, and 30.56 for H3 on the left side (p<0.005). The angle value was measured as 0 or negative value in 5 (20 %) of the H1 angle measurements made on the right side and 14 (56 %) on the left side. The H2 angle value was found to be smaller than the H1 angle in the skull 2 (8 %) on the right and 3 (12 %) on the left. There was no difference between the right and left sides in terms of vertical angular values. A significant difference was found between the right and left sides in the D1, D2, D4 distances (p<0.005). Six important anatomical features affecting angular values were encountered.

Para el tratamiento de la neuralgia del trigémino, se alcanza el foramen oval introduciendo una aguja en la mejilla. La termocoagulación se realiza con compresión con balón, administración de alcohol o radiofrecuencia. Aparte del método clásico, en teoría es posible alcanzar el foramen oval a través de la cavidad oral mediante el abordaje anterior. En nuestro estudio se tuvo como objetivo examinar horizontal y verticalmente los valores angulares que se deben dar a la aguja para alcanzar el foramen oval en el abordaje anterior. Se determinaron tres puntos de referencia en los lados derecho e izquierdo de 25 cráneos secos. Se insertó una varilla comenzando desde estos puntos de referencia y pasando por el centro del foramen oval. Se midieron los valores angulares verticales y horizontales de esta barra. Para cada foramen oval se realizaron mediciones de 3 ángulos verticales, 3 ángulos horizontales y 4 distancias. Hubo una diferencia significativa entre los lados derecho e izquierdo en términos de valores angulares horizontales. Valores medios de ángulos horizontales (en grados); a la derecha, 7,29 para H1, 12,15 para H2, 32,29 para H3; 1,26 para H1, 9,46 para H2 y 30,56 para H3 en el lado izquierdo (p<0,005). El valor del ángulo se midió como 0 o valor negativo en 5 (20 %) de las mediciones del ángulo H1 realizadas en el lado derecho y 14 (56 %) en el lado izquierdo. Se encontró que el valor del ángulo H2 era menor que el ángulo H1 en el cráneo 2 (8 %) a la derecha y 3 (12 %) a la izquierda. No hubo diferencia entre los lados derecho e izquierdo en términos de valores angulares verticales. Se encontró diferencia significativa entre el lado derecho e izquierdo en las distancias D1, D2, D4 (p<0,005). Se encontraron seis características anatómicas importantes que afectan los valores angulares.

Review of complications due to foramen ovale puncture.

We aim to evaluate the mechanisms responsible for complications during trigeminal rhizotomy via foramen ovale puncture. Ten dry skulls and 10 skull-base specimens were investigated in the present study. In cadaveric skull-base specimens, the anatomical relationships between the foramen ovale, mandibular nerve and Gasserian ganglion and the surrounding neurovascular structures were investigated intradurally. The distance between the foramen ovale and Gasserian ganglion was measured as 6 mm. The abducent nerve, adjacent to the anterior tail of the petrolingual ligament, was observed passing along the lateral wall of the cavernous sinus. Advancement of the catheter more than 10 mm from the foramen ovale is likely to damage the internal carotid artery and the abducent nerve at the medial side of the petrolingual ligament. Thermocoagulation of the lateral wall of the cavernous sinus may damage the cranial nerves by heat, giving rise to pareses.

Percutaneous radio-frequency mandibular nerve rhizotomy guided by CT fluoroscopy.

We describe a new method for radio-frequency mandibular nerve rhizotomy under CT fluoroscopy. A patient with cancer had severe intractable and drug-resistant pain in his left mandibular region. Because he had an anatomic deformity due to cancer invasion and radiation therapy, we planned a mandibular nerve rhizotomy under CT fluoroscopic imaging. The needle was advanced to the mandibular nerve just caudal to the foramen ovale under real-time CT fluoroscopy, avoiding the cancer region. Pain scores of the patient were reduced after the nerve rhizotomy, without any complications.

Posterior fossa reexploration for persistent or recurrent trigeminal neuralgia or hemifacial spasm: surgical findings and therapeutic implications.

OBJECTIVE: To evaluate the surgical findings and subsequent therapeutic implications of posterior fossa reexploration for persistent or recurrent trigeminal neuralgia (TN) or hemifacial spasm (HFS) after failed microvascular decompression (MVD). METHODS: Between December 1975 and October 1996, the senior author performed 31 reexplorations for failure or recurrence after MVD: 23 for TN and 8 for HFS. Records were analyzed retrospectively for evidence of vascular compression in primary and secondary operations, other pertinent intraoperative findings, intraoperative therapeutic interventions, and postoperative results and complications. RESULTS: The previously placed polyvinyl alcohol foam (Ivalon sponge; Unipoint Industries, High Point, NC) or Teflon implant (Teflon felt; CR Bard, Inc., Bard Implants Division, Billerica, MA) was found to be in good position in 100% of the patients (31 of 31 patients). New vascular compression from an arterial source was found in three patients during posterior fossa reexploration: one with TN and two with HFS. New vascular compression from a venous source was observed in one patient with HFS. A scarred Ivalon sponge or Teflon implant with apparent mass effect on the nerve root was identified in seven reexplorations. One bony source of compression was seen. No new compressive elements or other sources of root irritation were appreciated in 61% of reexplorations. Partial sensory trigeminal rhizotomy was performed in 83% of reexplorations for persistent or recurrent TN. Of eight patients undergoing reexploration for persistent or recurrent HFS, six sustained complications. CONCLUSION: Recurrent vascular compression was seldom identified during posterior fossa reexploration for failed MVD in patients with persistent or recurrent TN or HFS. The previously placed Ivalon sponge or Teflon implant was consistently found to be in good position. Partial sensory trigeminal rhizotomy is an often effective alternative in cases of recurrent TN when neurovascular compression is not identified. However, because of the relatively high incidence of complications associated with reexploration, we recommend other ablative or medical treatments for most patients after failed MVD for TN or HFS.

Trigeminal neuralgia and glossopharyngeal neuralgia: two orofacial pain syndromes encountered by dentists.

BACKGROUND: Dentists frequently evaluate patients for oropharyngeal pain that may or may not eventually be related to oral pathology. Two rare neurological disorders that present with severe orofacial pain are trigeminal neuralgia, or TN, and glossopharyngeal neuralgia, or GPN. Both are secondary to cranial nerve compression by arteries and veins at the point at which the nerves exit the pons and brainstem. RESULTS: The authors present the results for two series of patients treated for TN and GPN. Significant success can be seen after intracranial microvascular decompression for both disorders, with low complication rates. Short- and long-term outcomes depend on proper patient selection. CLINICAL IMPLICATIONS: It is important for practitioners to recognize these syndromes and properly refer patients to a neurosurgeon experienced in treating such disorders. This can help the dentist and patient avoid oral procedures that will not alleviate the painful symptoms.

Surgical treatment of trigeminal neuralgia.

TRIGEMINAL NEURALGIA, which is unilateral electric shock or knifelike pain occurring in one or more branches of the trigeminal nerve, is evoked by stimulation of the face, lips, or gums caused by activities such as shaving, brushing the teeth, or moving trigger zones. IT GENERALLY IS ACCEPTED that classic trigeminal neuralgia is a consequence of vascular compression and demyelination of the trigeminal nerve. Although medical therapy is available, it gradually becomes less effective because of the progressive nature of trigeminal neuralgia. MICROVASCULAR DECOMPRESSION of the trigeminal nerve to treat trigeminal neuralgia is discussed in this article. Perioperative care, expected course of recovery, and potential complications are described.

Anatomic study of the infraorbital foramen for radiofrequency neurotomy of the infraorbital nerve.

OBJECTIVE: To examine the anatomy of the infraorbital canal and foramen and the angles at which a radiofrequency probe must be directed to enter the infraorbital foramen and canal, as a guide to performing radiofrequency ablation of the infraorbital nerve in patients with relative or absolute contraindications to lesions of the trigeminal ganglion or posterior root. METHODS: Eleven cadaveric skulls were studied. The infraorbital nerve, after passing through the infraorbital foramen, enters the infraorbital canal and groove in the floor of the orbit before reaching the foramen rotundum. Small probes were placed through the foramen into the infraorbital canal, and pictures were taken in the anteroposterior and sagittal planes. The pictures were analyzed using the ImageTool program (University of Texas Health Science Center, San Antonio, TX) to calculate the anteroposterior and sagittal angles of the probe. The distances of the foramen from the midline, lateral edge of the anterior nasal aperture, and inferior orbital rim were examined. RESULTS: A probe introduced through the cheek from below and medial to the foramen and directed upward and laterally at an angle of approximately 22 degrees in the coronal plane and 120 degrees in the sagittal plane toward a point approximately 26 mm from the midline and 8 mm below the inferior orbital rim will penetrate the infraorbital foramen for placement of the probe's tip in the infraorbital canal. CONCLUSION: The coordinates for placement of the radiofrequency probe through the infraorbital foramen and into the infraorbital canal are reviewed, along with a discussion of pitfalls in radiofrequency ablation of the nerve.

Functional repair after dorsal root rhizotomy using nerve conduits and neurotrophic molecules.

Functional recovery after large excision of dorsal roots is absent because of both the limited regeneration capacity of the transected root, and the inability of regenerating sensory fibers to traverse the dorsal root entry zone. In this study, bioresorbable guidance conduits were used to repair 6-mm dorsal root lesion gaps in rats, while neurotrophin-encoding adenoviruses were used to elicit regeneration into the spinal cord. Polyester conduits with or without microfilament bundles were implanted between the transected ends of lumbar dorsal roots. Four weeks later, adenoviruses encoding NGF or GFP were injected into the spinal cord along the entry zone of the damaged dorsal roots. Eight weeks after injury, nerve regeneration was observed through both types of implants, but those containing microfilaments supported more robust regeneration of calcitonin gene-related peptide (CGRP)-positive nociceptive axons. NGF overexpression induced extensive regeneration of CGRP(+) fibers into the spinal cord from implants showing nerve repair. Animals that received conduits containing microfilaments combined with spinal NGF virus injections showed the greatest recovery in nociceptive function, approaching a normal level by 7-8 weeks. This recovery was reversed by recutting the dorsal root through the centre of the conduit, demonstrating that regeneration through the implant, and not sprouting of intact spinal fibers, restored sensory function. This study demonstrates that a combination of PNS guidance conduits and CNS neurotrophin therapy can promote regeneration and restoration of sensory function after severe dorsal root injury.

[Diagnosis and treatment of the patient with trigeminal neuralgia]. / Diagnóstico y tratamiento del paciente con neuralgia del trigémino.

Neuralgia of the trigeminus (NT) is the most common of cranial nerve neuralgias. Its diagnosis is entirely clinical and its most common form of presentation is well understood. Questions of differential diagnosis can emerge with certain entities such as atypical trigeminal neuralgia, short-duration unilateral neuralgiform cephalea of the trigeminus (SUNCT) arising from injection to the conjunctival, lacrimal or other glands, cluster headache, chronic paroxymal hemicrania, pain arising in the teeth and myofacial pain syndrome. The three main causative factors of NT are compression of the nerve root by an artery in the prepontine space, thereby creating an area of demyelinization, compression of the nerve by a tumor, and multiple sclerosis. The first is the most common of the three. NT can be classified as essential in 10 to 30% of patients. Recent advances in magnetic resonance (MR), and its advantages over other imaging systems, have made MR the diagnostic method of choice. The first treatment is medical and the basic drugs involved can be considered classic. Other therapies have been suggested in recent years, however, and should probably be studied further. Two substances stand out among those proposed: tocainide, an antiarrhythmic drug, and pimozide, an antipsychotic. Surgical treatment of NT can address either the cause (tumor or vascular compression) or symptoms, the latter being indicated when medical treatment fails. Surgery can be performed on peripheral nerves, on the gasserian ganglion and on the posterior fossa. The indications, outcomes and possible complications are quite different for each approach, making choice controversial.