Magnetic resonance neurography of the head and neck: state of the art, anatomy, pathology and future perspectives

Flexible Array for Cervical and Extraspinal (FACE) MR Neurography of the Occipital Nerves at 3T

This technical report describes use of a novel, conformable receive-only radiofrequency coil for 3T MR neurography in a cohort of patients with occipital neuralgia. Applying a submillimeter, isotropic 3D double-echo steady-state sequence, detailed visualization of the occipital nerves and associated pathologies could be achieved.

Compartmentalization of High Infratemporal Fossa in Oral Cavity Squamous Cell Carcinomas and Its Impact on Clinical Outcome

BACKGROUND

According to the 8th edition of the American Joint Committee on Cancer (AJCC), involvement of the masticator space and infratemporal fossa (ITF) in oral cancers indicates advanced disease (T4b), which is often considered unresectable. Previous studies have shown that the extent of ITF involvement influences management and outcomes. Therefore, to optimize management, T4b disease should be subclassified based on ITF involvement. Notably, infranotch disease has a more favorable prognosis compared to supranotch disease. Our study also observed that certain subsets of high anterior retroantral ITF involvement may be operable with favorable clinical outcomes. This study aims to derive a new image-based compartmentalization of high ITF involvement and assess its impact on the management and outcomes of oral head and neck squamous cell carcinoma (HNSCC) patients with high ITF involvement.

MATERIALS AND METHODS

This retrospective observational study included 154 non-metastatic, upfront unresectable locally advanced HNSCC patients who were fit for induction neoadjuvant chemotherapy (NACT). ITF involvement was classified into distinct compartments, and detailed staging of the primary tumor (T) and regional nodes (Ns) was performed. Clinical data, including patient demographics, treatment received, and follow-up notes, were documented. Prognosis was assessed using survival metrics: event-free survival (EFS), progression-free survival (PFS), and overall survival (OS). The ITF was categorized into the following compartments: compartment 1 (low ITF: medial pterygoid), compartment 2 (anterior high ITF: retroantral fat), compartment 3 (posterior high ITF), including 3a (paramandibular compartment: paramandibular fat/temporalis), 3b (muscle compartment: lateral pterygoid), and 3c (Perineural compartment: pterygopalatine fossa and pterygomaxillary fissure).

RESULTS

Of the 154 cases, 142 (92%) were classified as T4b, with 63 (40.9%) having high ITF involvement and 79 (55.6%) having low ITF involvement. Twelve cases had T4a disease, which was deemed unresectable due to extensive nodal involvement. Subcompartmentalization of the 63 high ITF cases revealed 26 (41.2%) with compartment 2 involvement, 17 (26.9%) with compartment 3a involvement, 11 (17.4%) with compartment 3b involvement, and 9 (14%) with compartment 3c involvement. Disease progression following NACT was significantly higher in compartment 3c, which showed a poor response (p = 0.007). Univariate analysis for PFS revealed similar outcomes for compartments 1 and 2 (p = 0.692), while compartment 3 demonstrated poorer outcomes (p = 0.033). Among thosehigh ITF involvement, compartment 3c had the worst PFS outcome (p = 0.03).

CONCLUSIONS

Baseline imaging plays a critical role in guiding individualized treatment and predicting clinical outcomes. Low ITF involvement and disease limited to the high retroantral fat compartment exhibit similar clinical outcomes. Among the posterior high ITF compartments, involvement of the pterygopalatine fossa and pterygomaxillary fissure (compartment 3c) is associated with the worst prognosis and poor response to chemotherapy. Subcompartmentalization of ITF involvement provides valuable prognostic information to tailor treatment strategies.

Preoperative evaluation of lingual cortical plate thickness and the anatomical relationship of the lingual nerve to the lingual cortical plate via 3T MRI nerve-bone fusion

OBJECTIVES

To evaluate the reliability of 3T MRI nerve-bone fusion in assessing the lingual nerve (LN) and its anatomical relationship to the lingual cortical plate prior to the impacted mandibular third molar (IMTM) extraction.

METHODS

The MRI nerve and bone sequences used in this study were 3D T2-weighted fast field echo (3D-T2-FFE) and fast field echo resembling a CT using restricted echo-spacing (FRACTURE), respectively. Both sequences were performed in 25 subjects, and the resulting 3D-T2-FFE/FRACTURE fusion images were assessed by 2 independent observers. Semi-quantitative analyses included assessments of overall image quality, image artefacts, nerve continuity, and the detectability of 5 intermediate points (IPs). Quantitative analyses included measurements of the lingual cortical plate thickness (LCPT), vertical distance (V1* and V2*), and the closest horizontal distance (CHD) between the LN and the lingual cortical plate. Reliability was evaluated using weighted Cohen's kappa coefficient (κ), intraclass correlation coefficient (ICC), and Bland-Altman plots. Differences in LCPT between 3D-T2-FFE/FRACTURE fusion images and cone-beam computed tomography (CBCT) were compared using independent samples t-tests or Mann-Whitney U tests.

RESULTS

The fusion images demonstrated that the LN continuity score was 3.00 (1.00) (good), with 88% (44/50) of LNs displayed continuously at the IMTM level. Intra-reader agreement for nerve continuity was moderate (κ = 0.527), as was inter-reader agreement (κ = 0.428). The intra-reader and inter-reader agreement for LCPT measurements at the neck, mid-root, and apex of the IMTM were all moderate (ICC > 0.60). Intra-reader agreements for V1*, V2*, and CHD were moderate to excellent (ICC = 0.904, 0.967, and 0.723, respectively), and inter-reader agreements for V1*, V2*, and CHD were also moderate to excellent (ICC = 0.948, 0.941 and 0.623, respectively). The reliability of LCPT measurements between 3D-T2-FFE/FRACTURE fusion and CBCT was moderate (ICC = 0.609-0.796).

CONCLUSIONS

The 3D-T2-FFE/FRACTURE fusion technique demonstrated potential feasibility for the identification of the LN and its relationship to the lingual cortical plate, as well as for the measurement of LCPT. This study has generated a dataset that is capable of simultaneously defining the LN and LCPT.

Use of Magnetic Resonance Neurography for Sensory Nerve Injuries of the Head and Neck

Background

Identification of peripheral nerve injuries of the head and neck can be challenging due to a broad spectrum of symptoms from neuropathic pain to headaches and migraine. This article aimed to present the clinical features and diagnostic workup of patients with acute and chronic peripheral nerve injuries of the head and neck using magnetic resonance neurography (MRN), to demonstrate potential advantages compared with conventional magnetic resonance imaging (MRI).

Methods

Patients who presented with suspected peripheral nerve injury were either referred for a conventional MRI or MRN. Patients who underwent nerve exploration for suspected nerve transection and/or neuroma formation on imaging were included in this study. Imaging findings were correlated with intraoperative observations.

Results

Four patients (3 women, 1 man, age range: 34-70 years) were included. Three subjects had a history of head and neck surgery and 1 experienced direct trauma to the medial eyebrow. Clinical symptoms included numbness, allodynia, positive Tinel sign, and pain relief following nerve blocks. Two patients underwent conventional MRI and 2 underwent MRN. MRI provided a vague indication of potential neuromas and failed to accurately depict their locations. MRN offered a comprehensive visualization of the entire nerve path, identifying nerve transection and neuromas, as well as precise location, dimensions, and relation to adjacent bones and muscles.

Conclusions

High-resolution 3-dimensional MRN provides clear visualization of acute and chronic peripheral nerve injuries of the head and neck region, facilitating early diagnosis of nerve injuries in this region and improving diagnostic accuracy, as well as surgical planning and execution.

Clinical Correlation of Oblique Magnetic Resonance Imaging for Cervical Foraminal Stenosis

Introduction The diagnosis of cervical foraminal stenosis is primarily clinical since imaging methods do not allow direct visualization of the foramen, limiting the usefulness of classic studies such as simple magnetic resonance imaging. The objective of the study was to correlate the clinical symptoms of patients with cervical foraminal stenosis with the images obtained from oblique cervical spine magnetic resonance imaging. Materials and methods A pilot study included patients diagnosed with cervical foraminal stenosis. Clinical evaluation and disability scales [Neck Disability Index (NDI), modified Japanese Orthopedic Association Scale (mJOA)], quality of life [Short Form-36 (SF-36)], and pain [visual analog scale (VAS)] were applied. Subsequently, oblique magnetic resonance imaging at 45° was performed with direct visualization of the left and right foramina, and stenosis grades were classified using the Park scale. Descriptive statistics and correlations between clinical scales and stenosis grades were performed. Results The sample consisted of 30 patients who met the inclusion criteria, with an average age of 56.37 ± 15.81 years. 50% (15/30) were female. The SF-36 mental component summary (MCS) scale reported an average of 40.23 ± 13.29 (range 15-70), SF-36 physical component summary (PCS) 40.23 ± 12.77 (range 19-65), NDI 28.90 ± 16.60 (min 3, max 80), mJOA 10.70 ± 3.04 (range 4-17). The correlation between the Park compression degree and age was significant (r = 0.735, p = 0.0001), indicating greater stenosis with increasing age. A significant correlation was also found between the mJOA clinical scale and Park compression degree (r = 0.41, p = 0.022). Conclusion A significant correlation was found between age and the degree of foraminal stenosis, as well as between foraminal stenosis according to the Park scale and the mJOA scale.

Contrast-free visualization of distal trigeminal nerve segments using MR neurography

BACKGROUND AND PURPOSE

The 3-dimensional cranial nerve imaging (CRANI) sequence may assist visualization of anatomical details of extraforaminal cranial nerves and aid in clinical diagnosis and preoperative planning. In this study, we investigated the feasibility of using a combined CRANI and magnetization-prepared rapid-acquisition gradient-echo (MPRAGE) imaging protocol to comprehensively identify trigeminal nerve projections.

METHOD

We evaluated the detection of distal regions of three branches of the ophthalmic nerve (V1), three branches of the maxillary nerve (V2), and five branches of the mandibular nerve (V3) in seven healthy adult subjects, with and without contrast injection. Nerve branches were rated on a 5-point scale by three observers. Interobserver reliability was studied using weighted kappa statistics and percentage agreement.

RESULTS

Among V1 and V2 branches, the frontal nerve and infraorbital nerve were most successfully identified (average rating of 3.9, agreement >80%) in precontrast MPRAGE images. In V3 branches, lingual and inferior alveolar nerves were most successfully identified (average rating of 3.9, agreement >80%) in precontrast CRANI images, with an excellent average rating. In all cases except one, interobserver reliability was rated good to excellent. The buccal nerve was the only branch with a low average interobserver rating. Gadolinium contrast did not improve nerve segment visualization in our study. This may relate to the specific anatomic regions assessed, gadolinium dose, postcontrast image timing, and lack of pathology.

CONCLUSION

A combined CRANI and MPRAGE protocol can be combined to visualize distal branches of V1, V2, and V3 and has potential for clinical use.

Assessment of traumatic mandibular nerve using MR neurography sequence: a preliminary study

BACKGROUND

Iatrogenic mandibular nerve damage resulting from oral surgeries and dental procedures is painful and a formidable challenge for patients and oral surgeons alike, mainly because the absence of objective and quantitative methods for diagnosing nerve damage renders treatment and compensation ambiguous while often leading to medico-legal disputes. The aim of this study was to examine discriminating factors of traumatic mandibular nerve within a specific magnetic resonance imaging (MRI) protocol and to suggest tangible diagnostic criteria for peripheral trigeminal nerve injury.

METHODS

Twenty-six patients with ipsilateral mandibular nerve trauma underwent T2 Flex water, 3D short tau inversion recovery (STIR), and diffusion-weighted imaging (DWI) acquired by periodically rotating overlapping parallel lines with enhanced reconstruction (PROPELLER) pulse sequences; 26 injured nerves were thus compared with contra-lateral healthy nerves at anatomically corresponding sites. T2 Flex apparent signal to noise ratio (FSNR), T2 Flex apparent nerve-muscle contrast to noise ratio (FNMCNR) 3D STIR apparent signal to noise ratio (SSNR), 3D STIR apparent nerve-muscle contrast to noise ratio (SNMCNR), apparent diffusion coefficient (ADC) and area of cross-sectional nerve (Area) were evaluated.

RESULTS

Mixed model analysis revealed FSNR and FNMCNR to be the dual discriminators for traumatized mandibular nerve (p < 0.05). Diagnostic performance of both parameters was also determined with area under the receiver operating characteristic curve (AUC for FSNR = 0.712; 95% confidence interval [CI]: 0.5660, 0.8571 / AUC for FNMCNR = 0.7056; 95% confidence interval [CI]: 1.011, 1.112).

CONCLUSIONS

An increase in FSNR and FNMCNR within our MRI sequence seems to be accurate indicators of the presence of traumatic nerve. This prospective study may serve as a foundation for sophisticated model diagnosing trigeminal nerve trauma within large patient cohorts.

Visualization of clinically silent, odontogenic maxillary sinus mucositis originating from periapical inflammation using MRI: a feasibility study

OBJECTIVES

Maxillary sinus mucositis is frequently associated with odontogenic foci. Periapical inflammation of maxillary molars and premolars cannot be visualized directly using radiation-based imaging. The purpose of this study was to answer the following clinical question: among patients with periapical inflammatory processes in the maxilla, does the use of magnetic resonance imaging (MRI), as compared to conventional periapical (AP) and panoramic radiography (OPT), improve diagnostic accuracy?

METHODS

Forty-two subjects with generalized periodontitis were scanned on a 3 T MRI. Sixteen asymptomatic subjects with mucosal swelling of the maxillary sinus were enrolled in the study. Periapical edema was assessed using short tau inversion recovery (STIR) sequence. Apical osteolysis and mucosal swelling were assessed by MRI, AP, and OPT imaging using the periapical index score (PAI). Comparisons between groups were performed with chi-squared tests with Yates' correction. Significance was set at p < 0.05.

RESULTS

Periapical lesions of maxillary premolars and molars were identified in 16 subjects, 21 sinuses, and 58 teeth. Bone edema and PAI scores were significantly higher using MRI as compared to OPT and AP (p < 0.05). Using the STIR sequence, a significant association of PAI score > 1 and the presence of mucosal swelling in the maxillary sinus was detected (p = 0.03).

CONCLUSION

Periapical inflammation and maxillary mucositis could be visualized using STIR imaging. The use of MRI may help detect early, subtle inflammatory changes in the periapical tissues surrounding maxillary dentition. Early detection could guide diagnostic criteria, as well as treatment and prevention.

3D CRANI, a novel MR neurography sequence, can reliable visualise the extraforaminal cranial and occipital nerves

OBJECTIVES

We aim to validate 3D CRANI, a novel high-field STIR TSE, MR neurography sequence in the visualisation of the extraforaminal cranial and occipital nerve branches on a 3-T system. Furthermore, we wish to evaluate the role of gadolinium administration and calculate nerve benchmark values for future reference.

METHODS

Eleven consecutive patients underwent MR imaging including the 3D CRANI sequence before and immediately after intravenous gadolinium administration. Two observers rated suppression quality and nerve visualisation using Likert scales before and after contrast administration. Extraforaminal cranial and occipital nerves were assessed. Nerve calibers and signal intensities were measured at predefined anatomical landmarks, and apparent signal intensity ratios were calculated.

RESULTS

The assessed segments of the cranial and occipital nerves could be identified in most cases. The overall intrarater agreement was 79.2% and interrater agreement was 82.7% (intrarater κ = .561, p < .0001; interrater κ = .642, p < .0001). After contrast administration, this significantly improved to an intrarater agreement of 92.7% and interrater agreement of 93.6% (intrarater κ = .688, p < .0001; interrater κ = .727, p < .0001). Contrast administration improved suppression quality and significant changes in nerve caliber and signal intensity measurements. Nerve diameter and signal intensity benchmarking values were obtained.

CONCLUSION

3D CRANI is reliable for the visualization of the extraforaminal cranial and occipital nerves. Intravenous gadolinium significantly improves MR neurography when applying this sequence. Benchmarking data are published to allow future assessment of the 3D CRANI sequence in patients with pathology of the extraforaminal cranial and occipital nerves.

KEY POINTS

• MR neurography using the 3D CRANI sequence is a reliable method to evaluate the extraforaminal cranial and occipital nerves. • Gadolinium contrast administration significantly improves suppression quality and nerve visualisation. • Benchmarking values including apparent signal intensity ratios and nerve calibers depend on contrast administration and might play an important role in future studies evaluating extraforaminal cranial and occipital neuropathies.

Dental MRI-only a future vision or standard of care? A literature review on current indications and applications of MRI in dentistry

MRI is increasingly used as a diagnostic tool for visualising the dentoalveolar complex. A comprehensive review of the current indications and applications of MRI in the dental specialities of orthodontics (I), endodontics (II), prosthodontics (III), periodontics (IV), and oral surgery (V), pediatric dentistry (VI), operative dentistry is still missing and is therefore provided by the present work.The current literature on dental MRI shows that it is used for cephalometry in orthodontics and dentofacial orthopaedics, detection of dental pulp inflammation, characterisation of periapical and marginal periodontal pathologies of teeth, caries detection, and identification of the inferior alveolar nerve, impacted teeth and dentofacial anatomy for dental implant planning, respectively. Specific protocols regarding the miniature anatomy of the dentofacial complex, the presence of hard tissues, and foreign body restorations are used along with dedicated coils for the improved image quality of the facial skull.Dental MRI poses a clinically useful radiation-free imaging tool for visualising the dentoalveolar complex across dental specialities when respecting the indications and limitations.

Posttraumatic Trigeminal Neuropathic Pain in Association with Dental Implant Surgery

Posttraumatic trigeminal neuropathy in association with dental implant surgery is preventable, and this should be the emphasis for all clinicians considering this treatment for a patient. Once the nerve injury and posttraumatic neuropathy with or without pain ensues, there is very little the clinician can do to reverse it and the high pain and permanency of the neuropathy will have a significant functional and psychological impact on the patient. Immediate implant removal is required, and home check should be routine for all cases. International diagnostic criteria are available and should be implemented in everyday practice.

Technical Update on MR Neurography

Imaging evaluation of peripheral nerves (PNs) is challenging. Magnetic resonance imaging (MRI) and ultrasonography are the modalities of choice in the imaging assessment of PNs. Both conventional MRI pulse sequences and advanced techniques have important roles. Routine MR sequences are the workhorse, with the main goal to provide superb anatomical definition and identify focal or diffuse nerve T2 signal abnormalities. Selective techniques, such as three-dimensional (3D) cranial nerve imaging (CRANI) or 3D NerveVIEW, allow for a more detailed evaluation of normal and pathologic states. These conventional pulse sequences have a limited role in the comprehensive assessment of pathophysiologic and ultrastructural abnormalities of PNs. Advanced functional MR neurography sequences, such as diffusion tensor imaging tractography or T2 mapping, provide useful and robust quantitative parameters that can be useful in the assessment of PNs on a microscopic level. This article offers an overview of various technical parameters, pulse sequences, and protocols available in the imaging of PNs and provides tips on avoiding potential pitfalls.

Facial Paresthesia, a Rare Manifestation of Hereditary Neuropathy With Liability to Pressure Palsies: A Case Report

Trigeminal sensory neuropathy can be caused by a variety of conditions, including local, traumatic, iatrogenic, or systemic causes. Diagnosis and management remain a challenge for maxillofacial surgeons and neurologists. Therefore, a good clinical examination and objective tests and imaging are needed when diagnosing patients who present with facial numbness. We present a case with spontaneous episodes of facial paresthesia. He was diagnosed with hereditary neuropathy with liability to pressure palsies (HNPP), a rare condition that affects the peripheral nerves. Only a few case reports that describe involvement of the cranial nerves in patients with HNPP were found in the literature, and facial paresthesia has not been previously reported.

Preoperative visualization of the lingual nerve by 3D double-echo steady-state MRI in surgical third molar extraction treatment

Objectives

To assess the lingual nerve (LN) visualization using a 3D double-echo steady-state MRI sequence (3D-DESS).

Materials and methods

Three readers prospectively evaluated the LN for its continuous visibility in 3D-DESS MRI in 19 patients with an indication for removal of mandibular impacted third molars, using a 5-point scale (4 = excellent to 0 = none). Six LN anatomical intermediate points (IP) were selected and checked for their detectability by a 4-point scale (4 = yes to1 = no). Inter- and intra-rater agreement was evaluated using intraclass correlation coefficient and percentage of agreement.

Results

The average nerve continuity score was 3.3 ± 0.46. In 35% of the cases, the entire course was continuously visible. In 10%, the proximal and 60%, the distal part of the nerve was not continuously visible. Inter- and intra-reader agreement was good (ICC = 0.76, ICC = 0.75). The average detectability score of all IP was 3.7 ± 0.41. From IP1 to IP5, the detectability was excellent; meanwhile, IP6 had lower visibility. The inter- and intra-reader percentage of agreement was 77% and 87%.

Conclusions

The 3D-DESS sequence allowed accurate and continuous visualization of the LN with high reproducibility in more than one-third of the patients. This could improve the preoperative clarification of the LN position and thereby reduce complications during dentoalveolar surgical interventions.

Clinical relevance

3D-DESS MRI might be beneficial in clinical scenarios where the second molar is elongated or presents a difficult rotational position while simultaneously having a close positional relationship to the third molar. Thereby, osteotomy performed more lingually, indicating extended lingual flap detachment may increase the risk of LN damage.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00784-021-04185-z.