Isolated sixth cranial nerve aplasia visualized with Fast Imaging Employing Steady-State Acquisition (FIESTA) MRI

Magnetic resonance imaging of the cranial nerves in congenital, traumatic, and vascular diseases: a pictorial essay

The cranial nerves, which represent extensions of the functional structures of the brain, traverse the head and neck. They are connected to various cranial structures and are associated with several diseases. An in-depth understanding of their complex anatomy and normal imaging appearance allows the examiner to identify and characterize abnormalities with greater precision. One important tool for evaluating the cranial nerves is contrast-enhanced magnetic resonance imaging, especially three-dimensional steady-state free precession sequences, which provide high soft-tissue and spatial resolution, despite the slenderness of the nerves. In most cases, imaging findings are nonspecific. Therefore, to narrow the differential diagnosis, it is necessary to take a full patient anamnesis, perform a focused physical examination and order laboratory tests. In this pictorial essay we review, illustrate and discuss, from a pathophysiological perspective, congenital, traumatic, and vascular diseases of the cranial nerves.

Advances in magnetic resonance imaging of orbital disease

Magnetic resonance imaging (MRI) is increasingly used by the orbital surgeon to aid in the diagnosis, surgical planning, and monitoring of orbital disease. MRI provides superior soft tissue detail compared with computed tomography or ultrasound, and advancing techniques enhance its ability to highlight abnormal orbital pathology. Diffusion-weighted imaging is a specialized technique that uses water molecule diffusion patterns in tissue to generate contrast signals and can help distinguish malignant from benign lesions. Steady-state free precession sequences such as Constructive Interference in Steady-State (CISS) and Fast Imaging Employing Steady-state Acquisition (FIESTA) generate highly detailed, 3-dimensional reconstructed images and are particularly useful in distinguishing structures adjacent to cerebral spinal fluid. Magnetic resonance angiography can be used to characterize vascular lesions within the orbit. New developments in magnetic field strength as well as the use of orbital surface coils achieve increasingly improved imaging resolution.

Usefulness of Preoperative Simulation in Skull Base Approach: A Case Report

Skull base approach is a neurosurgical challenge requiring dexterity of the operating surgeon for good postoperative outcome. In addition to the experience of the operating surgeon, adequate preoperative information of the tumor is necessary to ensure better outcome. In clinoid meningioma, it is sometimes difficult to determine its relationship with the surrounding structure and the feeding artery. Previously, preoperative simulation has been utilized to determine the intracranial course of the compressed nerves in relation to the petroclival meningioma. We report a case of clinoid meningioma where preoperative fusion of three dimensional computed tomography angiography (3D-CTA) and 3T-fast imaging employing steady-state acquisition (FIESTA) images was useful in determining the exact location of the feeding artery to devascularize the tumor and aid in surgery. Preoperative simulation with three-dimensional digital subtraction angiography (3D-DSA) and 3T-FIESTA fusion images can be a useful adjunct tool to supplement surgery and to train neurosurgical trainees.

Post-traumatic Unilateral Avulsion of the Abducens Nerve with Damage to Cranial Nerves VII and VIII: Case Report

Traumatic injuries of the abducens nerve as a consequence of facial and/or head trauma occur with or without associated cervical or skull base fracture. This is the first report on unilateral avulsion of the abducens nerve in a 29-year-old man with severe right facial trauma. In addition, he exhibited mild left facial palsy, and moderate left hearing disturbance. Magnetic resonance imaging (MRI) using fast imaging employing steady-state acquisition (FIESTA) revealed avulsion of left sixth cranial nerve. We recommend thin-slice MR examination in patients with abducens palsy after severe facial and/or head trauma.

Facial and vestibulocochlear nerve avulsion at the fundus of the internal auditory canal in a child without a temporal bone fracture

OBJECTIVE

To describe a case of facial, vestibular, and cochlear nerve avulsion secondary to blunt trauma without an associated temporal bone fracture.

STUDY DESIGN

Clinical capsule report.

SETTING

University hospital.

PATIENT

A 3.5-year-old girl presented with immediate facial nerve paralysis and complete deafness after being struck by an automobile. High-resolution computed tomography demonstrated a depressed occipital bone fracture with no visible fracture of the temporal bone. Magnetic resonance imaging sequence raised the question of VIIth nerve bundle discontinuity at the distal end of the internal auditory canal.

INTERVENTION

The patient underwent a posterior fossa craniotomy via a translabyrinthine approach 9 months after the initial injury, and facial and auditory nerve avulsion at the fundus was confirmed at the time of surgery. The proximal segment of the facial nerve had formed a traumatic neuroma, which was resected, and primarily anastomosed to the rerouted distal segment.

MAIN OUTCOME MEASURES

Facial nerve function.

RESULTS

Patient has regained facial function to Grade III/VI House-Brackmann with no asymmetry at rest.

CONCLUSION

An unusual pattern of injury is described. We suggest that in patients presenting with facial nerve paralysis secondary to blunt trauma, without an associated temporal bone fracture, high-resolution magnetic resonance imaging is recommended to evaluate internal auditory canal discontinuity of the VIIth and VIIIth nerve complexes. A potential mechanism of avulsion is explained.