3D-FT MRI of the facial nerve

Magnetic resonance imaging of the caudal portion of the digastric muscle in canine idiopathic facial neuropathy

Idiopathic is the most common etiology for acute onset of facial neuropathy in dogs with limited number of studies describing MRI characteristics. A retrospective, observational study was performed using archived records, aiming to describe the MRI features of the caudal portion of the digastric muscle in dogs diagnosed with idiopathic facial neuropathy and to determine correlation with prognosis. Client-owned dogs presented to a referral hospital between 2009 and 2019, diagnosed with unilateral idiopathic facial neuropathy and having undergone MRI, with images including the caudal portion of the digastric muscle, were included (n = 19). MRI appearance of the affected muscle, including degree of muscle atrophy, signal intensity, enhancement post-contrast, and enhancement characteristics of the affected facial nerve, was described and compared to the contralateral, clinically unaffected caudal portion of the digastric muscle. Correlation between MRI appearance and outcome at 1-month and 3-months following onset of clinical signs was investigated. The majority of patients demonstrated some degree of muscle atrophy (n = 17, 89%), hyperintensity in T2W (n = 17, 89%), and pre-contrast T1W (n = 15, 79%) images, as well as contrast enhancement of the affected muscle (n = 14, 74%) and affected facial nerve (n = 9, 47%). There was no statistically significant correlation between atrophy or enhancement of the affected caudal portion of the digastric muscle nor between enhancement of the affected facial nerve and outcome. Hyperintensity both in T2W images and pre-contrast T1W images was significantly correlated with a worse prognosis. Ensuring inclusion and evaluation of this muscle in MRI may therefore be indicated in canine idiopathic facial neuropathy.

Clinical significance of quantitative analysis of facial nerve enhancement on MRI in Bell's palsy

CONCLUSIONS

Quantitative analysis of the facial nerve on the lesion side as well as the normal side, which allowed for more accurate measurement of facial nerve enhancement in patients with facial palsy, showed statistically significant correlation with the initial severity of facial nerve inflammation, although little prognostic significance was shown.

OBJECTIVES

This study investigated the clinical significance of quantitative measurement of facial nerve enhancement in patients with Bell's palsy by analyzing the enhancement pattern and correlating MRI findings with initial severity of facial palsy and clinical outcome.

SUBJECTS AND METHODS

Facial nerve enhancement was measured quantitatively by using the region of interest on pre- and postcontrast T1-weighted images in 44 patients diagnosed with Bell's palsy. The signal intensity increase on the lesion side was first compared with that of the contralateral side and then correlated with the initial degree of facial palsy and prognosis.

RESULTS

The lesion side showed significantly higher signal intensity increase compared with the normal side in all of the segments except for the mastoid segment. Signal intensity increase at the internal auditory canal and labyrinthine segments showed correlation with the initial degree of facial palsy but no significant difference was found between different prognostic groups.

Arterial vascularization of the cranial nerves

We discuss the arterial supply of the cranial nerves from their exit out of the brain stem to their exit from the skull base. Four distinct groups can be differentiated from an embryologic and phylogenetic standpoint. Understanding the arterial supply to the cranial nerves and the potential anastomoses is paramount in the endovascular treatment of dural AV shunts and highly vascularized tumors of the skull base to avoid neurologic deficits.

Bell Palsy: Quantitative Analysis of MR Imaging Data as a Method of Predicting Outcome

PURPOSE

To assess the prognostic value of quantitative analyses of region-of-interest (ROI) magnetic resonance (MR) imaging data in patients with acute facial nerve palsy.

MATERIALS AND METHODS

In a single-blinded study, MR images were obtained in 39 patients (32 men and seven women; age range, 18-75 years; average age, 37.9 years) with acute facial nerve palsy. MR images were obtained before the 6th day of illness, on the first day of standard inpatient treatment with high-dose steroids. Signal intensity (SI) was measured at ROIs in each of five segments (internal auditory canal [IAC]; geniculate ganglion; and labyrinth, tympanic, and mastoid segments) of the intratemporal portion of the facial nerve and quantitatively analyzed. The SI measurements in the five segments were summed and divided by 100 to provide a basis for establishing an MR imaging index. SI increases and MR imaging indexes were compared with available clinical findings and electrophysiologic data.

RESULTS

Data for all 39 patients could be analyzed. The MR imaging index was significantly higher in patients with poor outcomes than in patients with favorable outcomes (specificity, 97%; sensitivity, 75%; P <.01). The SI increases in the IAC were significantly different between patients who progressed to full recovery (mean increase, 45.7%) and patients who developed chronic facial paralysis (mean increase, 156.5%) (sensitivity, 100%; specificity, 97%; P <.001). The results of differentiating between patients with good and those with poor outcomes on the basis of SI measurements in the IAC were found to be in complete agreement with electrophysiologic data.

CONCLUSION

Quantitative analysis of ROI MR imaging data is a valid method of predicting the outcome of acute facial nerve palsy during the first days after onset of symptoms and thus at a time when it is not yet possible to obtain valuable prognostic information by using electrophysiologic methods.

CT and MR imaging of the normal and pathologic conditions of the facial nerve

Computed tomography (CT) and magnetic resonance imaging (MRI) are well established imaging modalities to examine the facial nerve as well as the course of the facial nerve itself. High spatial resolution is guaranteed not only in the x- and y-axis, but also in the z-axis using multislice spiral CT. With this technique, reformatted multiplanar images in oblique planes, avoiding additional examinations in the coronal plane, facilitate the delineation of the facial nerve canal. This is beneficial in patients with temporal bone trauma, malformation or osseous changes. MR has a superior soft-tissue contrast to CT that enables imaging of the facial nerve itself. Therefore the normal facial nerve as well as pathologic changes of the facial nerve is readily visualized from the brain stem to the parotid gland. This review article presents anatomy, pathology and imaging strategies in the diagnostics of the facial nerve.

Magnetic resonance imaging of the facial nerve in children with idiopathic facial paralysis

The role of gadolinium-enhanced MRI (Gd-MRI) in the diagnosis of idiopathic facial paralysis (IFP) in children is not well defined. Fourteen children with IFP were evaluated to assess the use of Gd-MRI for the presence and pattern of enhancement and its usefulness in predicting the recovery of facial function. Six of 14 children had enhancement of the facial nerve on Gd-MRI, whereas 8 had none. Enhancement was noted in the tympanic, mastoid, and most commonly in the distal intracanalicular and labyrinthine segments. The average time from onset of paresis to recovery in patients with enhancement was 19.3 weeks, whereas in those with no enhancement, mean recovery time was 9.5 weeks (P = 0.003, t test). All 14 patients eventually had recovery to House-Brackmann grade I or II. Gd-MRI is not required for all children with IFP but may yield information about the time course of recovery of facial function.

Study of the inferior oblique muscle of the eye by MRI

The utility of the inferior oblique m. radioanatomical study by a FLASH 3D sequence in magnetic resonance imaging (MRI). Twenty eyes (ten healthy volunteers aged 21-32 years, without any history of significant ocular pathology) were explored by MRI (1 Tesla; cranial coil) and comparisons were made between spin echo (SE) T1 sequence (through the neuro-ocular and coronal planes; thickness of slices = 3 mm) and a gradient echo FLASH 3D sequence (thickness of slices = 1 mm). This enabled a mm by mm reformation of the inferior oblique m through the frontal-oblique plane, made possible by new SE T1 sequences through the same plane. Position, height, and signal of the m. were estimated. The mean frontal angle formed by the muscle and the sagittal axis measured 29 degrees for the right eye and 27 degrees for the left eye. The muscle was always identifiable in the reformation despite its thin dimensions: 1.9 mm (1.5 - 2.8) on the right and 2 mm (1.7 - 2.5) on the left, in low signal silhouetted by the high signal of orbital fat. Thus, thanks to mm by mm reconstructions using FLASH 3D sequence, a good radioanatomic study of the inferior oblique m. by MRI is possible. This could be useful particularly for the strabismus of children.

Serial Gadolinium-Enhanced Magnetic Resonance Imaging and Assessment of Facial Nerve Function in Bell's Palsy

Eleven patients with mild or moderate acute idiopathic peripheral facial palsy, so-called Bell's palsy, were serially examined by gadolinium-DTPA-enhanced MRI on mean days 11, 40, and 97 (third examination, n = 10) after the onset of palsy. Results of the clinical and neurophysiologic assessment of facial nerve function were compared with the gadolinium-enhanced MRI findings. Eight of the 11 patients demonstrated contrast enhancement of the facial nerve at the initial examination, but in 7 of them, the enhancement had disappeared by the time of the serial follow-up gadolinium-enhanced MRI scans. The disappearance of facial nerve enhancement was found to be related to clinical and neurophysiologic improvements in facial nerve function during recovery from Bell's palsy. The three patients whose scans were negative at the initial gadolinium-enhanced MRI examination had the same clinical severity of palsy, but initially they had milder neurophysiologic involvement than those who demonstrated enhancement; these three patients did not exhibit enhancement at serial follow-up scans. These findings indicate that the presence of enhancement at the initial MRI scan is not necessarily indicative of a poor prognosis for recovery.

Magnetic resonance neurography for cervical radiculopathy: a preliminary report

Magnetic resonance neurography was used to directly image cervical spinal nerves in patients with clinical and radiographic evidence of cervical radiculopathy. A magnetic resonance imaging phased-array coil system was used to obtain high-resolution coronal T1-weighted spin echo, coronal/axial T2-weighted fast spin echo with fat saturation, and coronal/axial fast short tau inversion recovery weighted images of the cervical spine and spinal nerves. Three patients with neck and upper extremity pain and one asymptomatic volunteer were studied. The T2-weighted and the fast short tau inversion recovery images demonstrated markedly increased signal in the proximal portion of the affected spinal nerves. In two patients, contrast-to-noise measurements of the affected spinal nerves showed a markedly increased intensity compared with that of the noninvolved spinal nerves. Our findings demonstrate that phased-array coils used in conjunction with magnetic resonance neurography sequences can detect signal abnormalities within compressed cervical spinal nerves in patients with corresponding radicular symptoms and findings. This technique may prove to be helpful in evaluating patients with multilevel disc and/or spondylotic disease of the cervical spine.

Gd-DPTA enhanced MRI in Bell's palsy and herpes zoster oticus: an overview and implications for future studies

Magnetic resonance imaging (MRI) is a new and important tool for use in diagnosing and investigating diseases affecting the facial nerve. In recent gadolinium-DTPA enhanced MRI (Gd-MRI) studies it has unequivocally been demonstrated that ipsilateral facial nerve contrast enhancement, predominantly in the meatal portion, is present in both Bell's palsy and herpes zoster oticus. In this overview, the results of MRI studies performed on patients with acute peripheral facial palsy, especially Bell's palsy and herpes zoster oticus, are discussed. The Gd-MRI pattern in Bell's palsy is very similar to that seen in herpes zoster oticus, and the findings reported so far support the theory that an inflammation may be the cause of the nerve injury in both cases. So far, however, Gd-MRI has not been helpful in evaluating the severity and/or prognosis of the facial palsy. Further studies employing improved techniques, including three-dimensional fast (or turbo) spin echo (3DFSE) MRI with heavily T2-weighted sections and high resolution three-dimensional Fourier transform (3DFT) MRI, need to be conducted in order to determine whether it is possible to follow the course of the disease and whether MRI and/or Gd-MRI are useful prognostic tools in the early stages of palsy.