Skull base CT: normative values for size and symmetry of the facial nerve canal, foramen ovale, pterygoid canal, and foramen rotundum

Digital subtraction angiography-guided peripheral nerve stimulation via the foramen rotundum for refractory trigeminal postherpetic neuralgia: a case report and literature review

Postherpetic neuralgia (PHN) is a debilitating complication of varicella-zoster virus infection. This case report presents a novel approach to treating refractory trigeminal maxillary postherpetic neuralgia using digital subtraction angiography (DSA)-guided peripheral nerve stimulation via the foramen rotundum. A 72-year-old female with severe, treatment-resistant pain underwent this intervention. The results demonstrated the disappearance of tactile allodynia, a significant reduction in oral analgesic requirements, and no observed complications or side effects during a 3-year follow-up period. This case highlights the potential effectiveness of DSA-guided peripheral nerve stimulation using a new dorsal root ganglion (DRG) stimulator as an alternative therapy for refractory trigeminal postherpetic neuralgia (TPHN).

Infratemporal Fossa Vascular Anatomy Pertinent to Percutaneous Access to the Foramen Ovale for Treatment of Trigeminal Neuralgia: A Comparison of Cadaveric Dissection and Computed Tomography Analysis

BACKGROUND

Trigeminal neuralgia may be treated via percutaneous access to the foramen ovale (FO). Vascular complications associated with the needle trajectory can result in serious morbidity and mortality. This study aimed to correlate the vascular relationships of the FO at the skull base via cadaveric dissections and computed tomography (CT).

METHODS

Two fresh cadaver heads were injected with red and blue latex to delineate arteries and veins. Neck and infratemporal fossa dissections were carried out to delineate the vascular relationships of the FO. High-resolution head CT images of adult patients undergoing neurosurgical evaluations or procedures were analyzed for distances and sizes of skull base foramina in the infratemporal fossa.

RESULTS

Three infratemporal fossa dissections (2 cadaveric specimens) were performed. Mean distance of FO to internal carotid artery was 2.4 ± 0.12 cm, and mean distance of FO to middle meningeal artery was 0.8 ± 0.16 cm. Head CT images of 52 patients (104 sides) with 1-mm axial slice thickness were analyzed. Area of the FO was 31.1 ± 9.6 mm². Distance of FO to internal carotid artery was 1.70 ± 0.31 cm, and distance of FO to middle meningeal artery was 0.73 ± 0.61 cm.

CONCLUSIONS

Cadaveric delineation of vascular structures in the infratemporal fossa correlates with head CT imaging and may be used to accurately plan percutaneous access to the FO. Inadvertent puncture of the extracranial internal carotid artery is nearly impossible with good technique. The most likely source of percutaneous vascular injury is the middle meningeal artery and distal branches of the maxillary artery.

Imaging of Developmental Skull Base Abnormalities

The skull base is a critical structure in the craniofacial region, supporting the brain and vital facial structures in addition to serving as a passageway for important structures entering and exiting the cranial cavity. This paper will review and highlight some of the embryology, developmental anatomy, including ossification, and related abnormalities of the anterior, central and posterior skull base using illustrative cases and tables. Pathologies such as dermoids/epidermoids, cephaloceles, nasal gliomas, glioneuronal heterotopias, various notochordal remnants, persistent craniopharyngeal canal, teratomas, platybasia, basilar invagination, clival anomalies and Chiari malformations will be discussed. Developmental pearls and pitfalls will also be highlighted.

CT Evaluation of Variations in the Middle Cranial Fossa Foramina: A Potential Guide for Skull Base Surgery

OBJECTIVES

To evaluate and classify the variations of foramen ovale (FO), foramen spinosum (FS).

METHODS

Six hundred fifty-eight computed tomographies (CTs) were evaluated by 2 observers. Foramen ovale was classified as oval, almond, round, and slit-like. Duplication, absence, and confluence for FS were noted. Bony outgrowths were categorized as tubercule, bony plate, and spine.

RESULTS

Oval shaped FO was the most common subgroup. Most common FS variation was the confluence with FO. Of bony outgrowths, tubercule-shaped were the most common type and spine-shaped ones were the least. Substantial agreement for bony plate and tubercule, almost excellent agreement for all the other parameters were found between 2 observers.

CONCLUSIONS

Foramen ovale called lobulated and had not classified previously was described in this study. Computed tomography is a reliable tool for anatomical evaluation of FO and FS, which would effect the methods of middle cranial fossa surgery. Thus, radiologists should be a pathfinder about the variations of these structures.

Surgery combined with iodine-125 interstitial brachytherapy for treatment of parotid adenoid cystic carcinoma: A single-institution experience

PURPOSE

The purpose of this study was to analyze the effectiveness and safety of the combination of surgery plus postoperative iodine-125 interstitial brachytherapy for treatment of adenoid cystic carcinoma (ACC) of the parotid.

METHODS AND MATERIALS

This study included a retrospective analysis of the data of patients who underwent postoperative iodine-125 interstitial brachytherapy for histology-confirmed ACC of the parotid between January 2002 and November 2018 in Peking University Hospital of Stomatology. Acute and long-term radiation-related toxicities were assessed by the criteria of the Radiation Therapy Oncology Group and European Organization for Research and Treatment of Cancer. Multivariate analysis was used to identify the factors affecting overall survival, disease-free survival (DFS), and distant metastasis-free survival (DMFS).

RESULTS

A total of 86 patients (53 women; median age 50 years, SD = 13.1) were included. Median followup was for 45.5 months. About half the patients (44/86, 51.3%) had clinical stage IV disease. Local recurrence occurred in 11 of 86 (12.8%) patients. No patient had nodal metastases in the followup period. The five- and 10-year DFS rates were 74.8% and 66.6%, respectively. The mean DMFS was 60.6 months. On multivariate analysis, preoperative facial palsy, type of surgery, perineural spread (PNS), and distant metastases were independent prognostic factors for DFS; preoperative facial palsy, nodal metastases, and PNS were independent prognostic factors for overall survival; and preoperative facial palsy, type of surgery, PNS, and pathological type were independent prognostic factor for DMFS.

CONCLUSIONS

The combination of surgery and iodine-125 interstitial brachytherapy appears to be an effective and safe treatment for primary ACC of the parotid.

Biomechanical analysis of skull trauma and opportunity in neuroradiology interpretation to explain the post-concussion syndrome: literature review and case studies presentation

Traumatic head injuries are one of the leading causes of emergency worldwide due to their frequency and associated morbidity. The circumstances of their onset are often sports activities or road accidents. Numerous studies analysed post-concussion syndrome from a psychiatric and metabolic point of view after a mild head trauma. The aim was to help understand how the skull can suffer a mechanical deformation during a mild cranial trauma, and if it can explain the occurrence of some post-concussion symptoms. A multi-step electronic search was performed, using the following keywords: biomechanics properties of the skull, three-dimensional computed tomography of head injuries, statistics on skull injuries, and normative studies of the skull base. We analysed studies related to the observation of the skull after mild head trauma. The analysis of 23 studies showed that the cranial sutures could be deformed even during a mild head trauma. The skull base is a major site of bone shuffle. Three-dimensional computed tomography can help to understand some post-concussion symptoms. Four case studies showed stenosis of jugular foramen and petrous bone asymmetries who can correlate with concussion symptomatology. In conclusion, the skull is a heterogeneous structure that can be deformed even during a mild head trauma.

Towards an early 3D-diagnosis of craniofacial asymmetry by computing the accurate midplane: A PCA-based method

BACKGROUND AND OBJECTIVE

Craniofacial asymmetry is a common growth disorder often caused by unilateral chewing. Although an early orthodontic treatment would avoid surgical procedures later in life, the uncertainty of defining the accurate sagittal midplane potentially leads to misdiagnosis and therefore inaccurate orthodontic treatment plans. This novel study aims to 3D-diagnose craniofacial complex malformations in children with unilateral crossbite (UXB) considering a midplane which compensates the asymmetric morphology.

METHODS

The sagittal midplane of 20 children, fifteen of whom exhibited UXB, was computed by a PCA-based method which compensates the asymmetry mirroring the 3D models obtained from cone-beam computed tomography data. Once determined, one side of the data was mirrored using the computed midplane to visualize the malformations on the hard and soft tissues by 3D-computing the distances between both halves. Additionally, 31 skull's landmarks were manually placed in each model to study the principal variation modes and the significant differences in the group of subjects with and without UXB through PCA and Mann-Whitney U test analyses respectively.

RESULTS

Morphological 3D-analysis showed pronounced deformities and aesthetic implications for patients with severe asymmetry (jaw deviation > 0.8 mm) in whole craniofacial system, while initial signs of asymmetry were found indistinctly in the mandible or maxilla. We detected significant (p < 0.05) malformations for example in mandibular ramus length (0.0086), maxillary palate width (0.0481) and condylar head width (0.0408). Craniofacial malformations increased the landmarks' variability in the group of patients with UXB over the control group requiring 8 variation modes more to define 99% of the sample' variability.

CONCLUSIONS

Our findings demonstrated the viability of early diagnosis of craniofacial asymmetry through computing the accurate sagittal midplane which compensates the individual's asymmetrical morphology. Furthermore, this study provides important computational insights into the determination of craniofacial deformities which are caused by UXB, following some empirical findings of previous clinical studies. Hence, this computational approach can be useful for the development of new software in craniofacial surgery or for its use in biomedical research and clinical practice.

Key anatomical landmarks for middle fossa surgery: a surgical anatomy study

OBJECTIVE

Middle fossa surgery is challenging, and reliable surgical landmarks are essential to perform accurate and safe surgery. Although many descriptions of the middle fossa components have been published, a clinically practical description of this very complex anatomical region is lacking. Small structure arrangements in this area are often not well visualized or accurately demarcated with neuronavigation systems. The objective is to describe a "roadmap" of key surgical reference points and landmarks during middle fossa surgery to help the surgeon predict where critical structures will be located.

METHODS

The authors studied 40 dry skulls (80 sides) obtained from the anatomical board at their institution. Measurements of anatomical structures in the middle fossa were made with a digital caliper and a protractor, taking as reference the middle point of the external auditory canal (MEAC). The results were statistically analyzed.

RESULTS

The petrous part of the temporal bone was found at a mean of 16 mm anterior and 24 mm posterior to the MEAC. In 87% and 99% of the sides, the foramen ovale and foramen spinosum, respectively, were encountered deep to the zygomatic root. The posterior aspect of the greater superficial petrosal nerve (GSPN) groove was a mean of 6 mm anterior and 25 mm medial to the MEAC, nearly parallel to the petrous ridge. The main axis of the IAC projected to the root of the zygoma in all cases. The internal auditory canal (IAC) porus was found 5.5 mm lateral and 4.5 mm deep to the lateral aspect of the trigeminal impression along the petrous ridge (mean measurement values). A projection from this point to the middle aspect of the root of the zygoma, being posterior to the GSPN groove, could estimate the orientation of the IAC.

CONCLUSIONS

In middle fossa approaches, the external acoustic canal is a reliable reference before skin incision, whereas the zygomatic root becomes important after the skin incision. Deep structures can be related to these 2 anatomical structures. An easy method to predict the location of the IAC in surgery is described. Careful study of the preoperative imaging is essential to adapt this knowledge to the individual anatomy of the patient.

Personalized needle modification for CT-guided percutaneous infrazygomatic radiofrequency ablation of the maxillary nerve through the foramen rotundum in order to treat V2 trigeminal neuralgia

Background: The computed tomography (CT)-guided radiofrequency ablation (RFA) of the maxillary nerve (V2) via foramen rotundum (FR) approach has been reported to offer the highest rates of pain relief in V2 trigeminal neuralgia (TN). However, the access to FR may be obstructed by the greater wing of the sphenoid bone.

Objectives: We report on an optimized CT-guided percutaneous infrazygomatic of maxillary nerve through the foramen rotundum (FR) to treat V2 trigeminal neuralgia (TN) using personalized RFA needles based on patient’s individual CT-image parameters.

Patients and methods: 176 patients with isolated V2 TN were included. If the entry of the percutaneous needle into the FR canal was blocked by the greater wing of the sphenoid bone, straight RFA needles was bent at the tip with an angle α (the angle between the straight line from the external opening of FR to the skin entry point and the long axis of the FR canal). The maxillary nerve RFA was performed after confirmation with electrophysiological tests. Pain relief in the V2 territory and TN recurrence rate were followed for up to 60 months.

Results: Fifty-two patients (29.55%) required needle bending. The maxillary nerve thermal RFA resulted in analgesia in the V2 territory without affecting the V1 or V3 zone. TN recurrence rate at 6, 12, 24, 36, 48 and 60 months was 2.55%, 7.64%, 17.20%, 24.41%, 30.28% and 33.77%, respectively.

Conclusion: The personalized needle modification technique for maxillary nerve RFA through FR is safe and effective to treat V2 TN.

Computer-Assisted Design Template Guided Percutaneous Radiofrequency Thermocoagulation through Foramen Rotundum for Treatment of Isolated V2 Trigeminal Neuralgia: A Retrospective Case-Control Study

Objective

Radiofrequency thermocoagulation (RFT) through the foramen rotundum has emerged as an alternative for treatment of isolated V2 trigeminal neuralgia. But puncture of the foramen rotundum is difficult and time-consuming. In current study, we introduced the application of a computer-assisted design (CAD) template to guide foramen rotundum cannulation. Meanwhile, we assessed its safety and efficacy in the treatment of isolated V2 trigeminal neuralgia.

Methods

From November 2015 to August 2017, thirty-eight patients with isolated V2 trigeminal neuralgia were treated with computed tomography- (CT-) guided RFT through the foramen rotundum in our institution. All cases were reviewed, and patients were divided into the experimental group (n=17, puncture with a CAD template) and control group (n=21, free-hand puncture) according to the puncture method used. The puncture times, duration of puncture, and duration of operation were collected. The outcome of pain remission was evaluated utilizing the Barrow Neurological Institute's (BNI) pain score. Complications and recurrence of pain were also recorded. Data were compared between groups.

Results

The rate of one-time successful puncture in the experimental group was obviously higher than that in the control group. Mean puncture times in the experimental group was fewer. Average duration of puncture and operation in the experimental group was also shorter than that in the control group. All patients experienced good pain remission (BNI Class I or II) postoperatively. At four follow-up points (7 days, 3 months, 6 months, and 12 months after operation), there was no significant difference in good pain relief rate between the two groups. Meanwhile, no significant difference was found in complications.

Conclusions

CAD template is a safe and precise navigation instrument for RFT treatment of isolated V2 trigeminal neuralgia via the foramen rotundum. Therefore, this novel tool is worthy of clinical promotion.

Visualization of the vidian canal and nerve using magnetic resonance imaging

BACKGROUND AND PURPOSE

Few studies have investigated the vidian nerve (VN) and vidian canal (VC) with the use of magnetic resonance imaging (MRI). The present study aimed to characterize the VC and VN using MRI.

MATERIALS AND METHODS

A total of 91 patients underwent thin-sliced, contrast MRI. The course of the VC and VN and the relationships with relevant structures were analyzed.

RESULTS

The VC was identified in 95% of axial images on the right side and in 93% on the left. The course of the VC was delineated in 99% of serial coronal images on both sides. The VN location in the VC was highly variable. The course of the VC and transmitting VN was delineated in 95% of sagittal images on the right side and in 91% on the left. The mean length of the VC was 19.8 mm on the right side and 19.3 mm on the left. Topographical relationships between the anterior genu of the petrous internal carotid artery and the posterior end of the vidian canal could be classified into three types. Of these, the type terminating at the level of the petrous carotid was the most predominant, comprising 76% of 182 sides. The course of the VC and transmitting VN could be classified into four types. The straight type was the most predominant and was found in 41%.

CONCLUSIONS

The VC and transmitting VN are structures with variable morphologies. Contrast MRI is useful for delineating the VC and VN.

A Pilot Study to Investigate the Relationship Between Interaural Differences in Temporal Bone Anatomy and Normal Variations in Caloric Asymmetry

PURPOSE

This study assesses interaural differences in temporal bone anatomy in subjects with normal caloric findings.

METHOD

Eligible patients included those referred to the Duke University Medical Center otology clinic complaining of dizziness, with a head computed tomography scan and caloric stimulation results within normal ranges (inter-ear difference ≤ 10% or < 25% unilateral weakness). Three-dimensional reconstructions of computed tomography scans in 11 patients were used to calculate the surface area and volume of lateral semicircular canals (LSCCs), mastoid airspaces, mastoid bones, and internal auditory canal diameter and circumference. Percent differences in interaural temporal bone anatomy (i.e., left-to-right asymmetry) were analyzed and correlated with warm caloric inter-ear difference (WCD) and clinically indicated caloric predictor asymmetry.

RESULTS

A multivariate model predicting WCD from 9 interaural anatomic variables demonstrated a Pearson's coefficient of 0.999. A similarly constructed model of the clinically indicated caloric predictor demonstrated a Pearson's coefficient of 0.999. The univariate correlation was strongest for WCD versus Proctor internal auditory canal diameter (r = 0.476; p = .139) and WCD versus lateral semicircular canal surface-area-to-volume ratio (r = -0.474; p = .141).

CONCLUSIONS

This pilot study provides multivariate models that predict caloric asymmetry in subjects without vestibular pathologic findings per caloric testing, based on interaural differences across variables of the temporal bone anatomy.

SUPPLEMENTAL MATERIAL

https://doi.org/10.23641/asha.5895988.

Three-dimensional analysis of cranial base morphology in patients with hemifacial microsomia

BACKGROUND

Many researchers have studied the relationship between facial asymmetry and cranial base morphology, but they have failed to reach a consensus. In this study, we aimed to verify whether the cranial base is involved in hemifacial microsomia (HFM).

METHODS

We included 66 patients with HFM who were treated at the Plastic and Reconstructive Surgery Department of Shanghai Ninth People's Hospital from January 2013 to October 2016. The patients were divided into three groups according to Pruzansky and OMENS classifications, separately. The controls were 20 patients diagnosed with mandibular angle hypertrophy but with no facial asymmetry. Angular and linear measurements of the cranial base were obtained for all patients.

RESULTS

The two classification methods yielded similar results. The intersection angle between two planes showed differences in the severe group. In the moderate and severe groups, the middle and posterior cranial angles were significantly different and the CIP and SP lengths were shorter in the affected side. Landmarks such as the carotid canal and internal acoustic canal could be considered as references.

CONCLUSIONS

The cranial base is involved in hemifacial microsomia. This relationship supports the hypothesis of HFM pathogenesis and opens new avenues to classification methods.

Novel Method of Measuring Canal Dehiscence and Evaluation of its Potential as a Predictor of Symptom Outcomes After Middle Fossa Craniotomy

BACKGROUND

Superior semicircular canal dehiscence (SSCD) is an osseous defect of the arcuate eminence of the petrous temporal bone. Strategies for measuring dehiscence size are variable, and the usefulness of such parameters remains in clinical equipoise.

OBJECTIVE

To present a novel method of measuring dehiscence volume and to evaluate its potential as a predictor of symptom outcomes after surgical repair of SSCD.

METHODS

High-resolution computed tomographic temporal bone images were imported into a freely available segmentation software. Dehiscence lengths and volumes were ascertained by independent authors. Inter-rater observer reliability was assessed using Cronbach's alpha. Correlation and regression analyses were performed to evaluate for relationships between dehiscence size and symptoms (pre- and post-operative).

RESULTS

Thirty-seven dehiscences were segmented using the novel volumetric assessment. Cronbach's alpha for dehiscence lengths and volumes were 0.97 and 0.95, respectively. Dehiscence lengths were more variable as compared to dehiscence volumes (σ2 8.92 vs σ2 0.55, F = 1.74). The mean dehiscence volume was 2.22 mm3 (0.74, 0.64-0.53 mm3). Dehiscence volume and headache at presentation were positively correlated (Rpb = 0.67, P = .03). Dehiscence volume and vertigo improvement after surgery were positively correlated, although this did not reach statistical significance (Rpb = 0.46, P = .21).

CONCLUSION

SSCD volumetry is a novel method of measuring dehiscence size that has excellent inter-rater reliability and is less variable compared to dehiscence length, but its potential as a predictor of symptom outcomes is not substantiated. However, the study is limited by low power.

Enlargement of the infraorbital canal following Caldwell-Luc surgery

OBJECTIVES

The infraorbital canal (IOC), which runs in the roof of the maxillary sinus, is a useful anatomical landmark for the infraorbital nerve (ION) on computed tomography (CT) images. Enlargement of the IOC on CT images is thought to be a pathological state that usually affects the ION. However, we have frequently observed enlargement of the IOC in patients with a history of radical surgery of the maxillary sinus: so-called Caldwell-Luc (CL) surgery. In this study, the size of the IOC of the maxillary sinus was compared between patients with a history of CL surgery (post-CL IOCs) and those with no history of CL surgery (control IOCs).

METHODS

A total of 347 consecutive patients who underwent facial CT from January 2014 to October 2014 for various indications were evaluated. After excluding groove-type IOCs and IOCs with pathological lesions that could affect their diameters, 47 post-CL IOCs in 26 patients were finally compared with 504 control IOCs in 252 patients. To evaluate IOC size, the short-axis diameter of the IOC was measured on a reconstructed coronal image at the level of the posterior pole of the eyeball.

RESULTS

The short-axis diameters of the post-CL IOCs and control IOCs were 3.0 ± 0.6 and 1.4 ± 0.3 mm, respectively (p < 0.005).

CONCLUSIONS

The short-axis diameters of post-CL IOCs are significantly enlarged (approximately double the diameter) compared to those of control IOCs.

Clinical anatomy of the orbitomeningeal foramina: variational anatomy of the canals connecting the orbit with the cranial cavity

PURPOSE

In addition to the optic canal and the superior orbital fissure, orbits are connected with the cranial cavity via inconstant canals including the orbitomeningeal foramen. This study has been carried out in order to define many anatomical and radiological details of the orbitomeningeal foramen that are relevant in the clinical practice.

METHODS

Almost 1000 skulls and 50 computerized tomographies were examined to determine incidence, number, length, and caliber of the orbitomeningeal foramen as well as the topography of their orbital and cranial openings. A retrospective study of angiographies carried out on more than 100 children was performed to look for arteries candidate to run through the orbitomeningeal foramen.

RESULTS

Orbitomeningeal foramina were detected in 59.46% of skulls and in 54% of individuals by computerized tomography. Orbits with two to five foramina were found. Canals were classified as M-subtype or A-subtype depending on their cranial opening. Large foramina, with the caliber ranging between 1 and 3 mm, were found in 12.17% of orbitomeningeal foramen-bearing orbits. By computed tomography the average caliber measured 1.2 ± 0.3 and 1.5 ± 0.5 mm (p < 0.005) at the orbital and cranial openings, respectively (p < 0.005). Angiographies showed meningo-lacrimal and meningo-ophthalmic arteries, meningeal branches of the lacrimal and supraorbital arteries, and some unidentified arteries that could pass through the orbitomeningeal foramina.

CONCLUSIONS

Orbitomeningeal foramina are a common occurrence. When large they may house important arteries that can be the source of severe bleedings during deep dissection of the lateral wall of the orbit. Orbital surgeons should be aware of their existence.

The morphology and morphometry of the fetal fallopian canal: a microtomographic study

Background

The canal for facial nerve (the fallopian canal, FC) is a bony structure passing through the petrous part of the temporal bone. The anatomy of this demanding and important for oto- and neurosurgeons structure is well described in literature. Among several studies on radiological anatomy of this region, still little papers focus on the developmental measurements in prenatal period.

Aim

Assessment of a microtomographic appearance of FC and dimensions based on available landmarks.

Method

The study was performed on 22 fetal temporal bones aged 16–27 Hbd. Specimens were scanned in micro-CT scanner. Length (FC1, FC2) and width (FC1W, FC2W) of the labyrinthine and tympanic portions of FC, angle of the first curve of FC (A1-2), length of the internal acoustic meatus (IAM), distance from FC to the basal cochlear turn (BCT) and to the lateral semicircular canal (LSC) were measured.

Results

The paper discusses problems and a value of micro-CT in neuroanatomical studies. FC was found in 20/22 cases. Average value of all distances measured was: FC1 1.38 ± 0.35 mm; FC2 6.68 ± 1.34 mm; FC1W 1.07 ± 0.1 mm; FC2W 1.25 ± 0.13 mm; A1-2 87.24 ± 4.05°; IAM 4.89 ± 0.60 mm; BCT 0.35 ± 0.05 mm; LSC 0.55 ± 0.05 mm.

Conclusions

Labyrinthine portion starts to ossify between 16th and 18th weeks of gestation and tympanic portion is fully ossified only after 20th week. Labyrinthine and tympanic portion of FC and the IAM elongate with age, whereas the angle of the first curve of FC and the distances to the BCT and the LSC remain stable and present no correlation with age.

CT-guided percutaneous infrazygomatic radiofrequency neurolysis through foramen rotundum to treat V2 trigeminal neuralgia

OBJECTIVE

Percutaneous radiofrequency thermocoagulation or neurolysis of Gasserian ganglion through foramen ovale (FO) is the classical approach to treat trigeminal neuralgia (TN). However, it has been technically challenging when individual trigeminal sub-branch nerve block is desired through this approach. We have thus developed a novel computed tomograph-guided technique to block the V2 trigeminal nerve through foramen rotundum (FR). With this technique, we have conducted a study of 27 patients with isolated V2 TN. We hypothesize that this new technique will have comparable clinical outcome with the conventional FO approach.

DESIGN

Prospective study.

SETTING

Academic hospitals.

SUBJECTS

Twenty-seven patients with isolated classical V2 TN were enrolled and divided into FO group (N = 12) and FR group (N = 15).

METHODS

Numeric Rating Scale (NRS) scores for facial pain, at pretreatment, immediate postoperative, postoperative 1 day, and 1, 6, and 12 months were recorded. The primary clinical outcome (successful pain relief with 50% or more reduction in NRS) and secondary adverse clinical outcome (hematoma, facial numbness, masticatory weakness, and corneal involvement) were compared and analyzed.

RESULTS

Both groups have good immediate and sustained pain relief. However, when compared with the FO group, the FR group is associated with shorter procedural time (29.2 ± 9.3 vs 45.4 ± 22.13 minutes, P < 0.05), has less nonspecific block in V1 and V3 dermatomes, and has fewer adverse outcomes including masticatory weakness (0/15 vs 5/12) and corneal perforation (0/12 vs 1/15).

CONCLUSIONS

We have developed a novel technique to selectively block the V2 trigeminal nerve at FR. This novel FR approach may be a good alternative to the classical FO approach when an isolated V2 branch block is desired.

Transcranial segment of the trigeminal nerve: macro-/microscopic anatomical study using sheet plastination

BACKGROUND

Trigeminal neuralgia (TN) may be caused by the mechanical compression of the trigeminal nerve. In the studies on the location of mechanical irritation and entrapment of the nerve, attention has been paid mostly to vascular structures in the subarachnoid space. Few studies have explored the relationship between the trigeminal nerve and its surrounding structures along its course in the skull base. The aim of this study was to examine and trace the root, ganglion and three divisions of the trigeminal nerve and their relationships with surrounding soft and bony structures in the skull base, and to identify the likely mechanical compression points.

METHODS

A total of 26 adult cadavers (ten females, 16 males; age range, 45-81 years) were examined in this study, eight for dissection and 16 for sheet plastination study.

RESULTS

Anatomical structures that may make the trigeminal nerve susceptible to entrapment in the skull base were located at (1) the inferolateral edge of the mouth of Meckel's cave, (2) the middle cranial fossa dura and the lateral wall of the anterior intracavernous portion of the internal carotid artery, (3) the ridge of the medial wall of the foramen rotundum, and (4) the twisted periosteum and venous plexus of the foramen ovale.

CONCLUSION

This study identified four likely mechanical compression points along the course of the trigeminal nerve in the skull base. Knowledge of these TN-susceptible sites may be useful to both skull base surgeon and TN-animal model researcher, particularly when they study TN without vascular compression.

Gabriel Falloppius (1523-1562) and the facial canal

Gabriel Falloppius is known for his contributions to anatomy. Indeed, many anatomic structures bear his name, such as the Fallopian tubes, and his descriptions often contradicted those of other notable anatomists, such as Galen and Andreas Vesalius. In his textbook "Observationes Anatomicae," he described for the first time the structures of the ear, eye, and female reproductive organs, and elucidated the development of the teeth. Furthermore, Falloppius described the facial canal. The objectives of this paper are to provide an overview of Falloppius's life and to discuss the clinical relevance of the facial canal as understood from his description of this anatomic structure.