Galdino E. Valvassori

The Large Vestibular Aqueduct Syndrome

It has long been known that abnormally large vestibular aqueducts may accompany congenital malformations of the cochlea and semicircular canals. Recently, enlargement of the vestibular aqueducts as the sole radiographically detectable inner ear anomaly has been recognized as a distinct pattern of congenital inner ear malformation. Patho‐genesis of the large vestibular aqueduct syndrome probably stems from an early derangement in the embryogenesis of the endolymphatic duct. This anomaly appears to be relatively common in children with sensorineural hearing loss and is probably significantly underdiagnosed. Hearing loss is typically bilateral and progressive, with stepwise rather than fluctuant hearing decrements often triggered by relatively minor head trauma. A review of 17 patients (33 ears) revealed an average hearing level at presentation of 57 dB with a speech discrimination score of 66%. Considerable variability exists in hearing level among affected ears, ranging from normal hearing (4%) to profound deafness (39%). In 12 patients (23 ears) with an average long‐term follow‐up of 7.3 years, the hearing loss progressed by an average of 25 dB, with a drop of 29% in speech discrimination over the period of observation. An endolymphatic to subarachnoid shunt was performed on seven ears in an effort to stabilize hearing. Four of these ears had a substantial immediate postoperative drop in hearing. For this reason, endolymphatic sac surgery is not recommended for patients with this deformity.The radiographic observation of 50 patients, each having an enlarged (greater than 1.5 mm. diameter) vestibular aqueduct, are analyzed. In addition to the aqueduct other associated inner ear anomalies have been identified in 60% of this population including: enlarged vestibule (14); enlarged vestibule and lateral semicircular canal (7); enlarged vestibule and hypoplastic cochlea (4); and hypoplastic cochlea (4). The large equeduct then presumably represents an arrested phase of inner ear development common to all 50 cases. Only 8 of these cases may fall into the Mondini or Mondini-Alexander classification wherein cochlear abnormalities have been identified. The size of the aqueduct ranged from 1.5 to 8 mm. in the anteroposterior diameter; the clinical incidence is 50 in 3700 consecutive cases referred for inner ear tomography. Bilateral involvement is twice as common as unilateral with a female to male predominance of 3:2. Most cases are associated with congenital hearing losses.

Interpretation of anatomic variations of computed tomography scans of the sinuses: A surgeon's perspective

Four hundred computed tomography (CT) scans of patients undergoing endoscopic sinus surgery were studied with particular attention to anatomic variations. Six specific variations were identified that may predispose the surgeon to inadvertent penetration of the orbit or anterior cranial cavity. These anatomic variants are: 1. lamina papyracea lies medial to the maxillary sinus ostium; 2. maxillary sinus hypoplasia; 3. fovea ethmoidalis abnormalities, such as low or sloping fovea and encephaloceles; 4. lamina papyracea dehiscence resulting in herniation of orbital content into the ethmoids; 5. sphenoid sinus wall variations such as septa attached to the carotid covering, and penetration of the sphenoid by the internal carotid artery or optic nerve; 6. sphenoethmoid cells (Onodi cells), the most posterior ethmoid cells pneumatizing lateral and superior to the sphenoid and intimately associated with the optic nerve.

Bicaudate index in computerized tomography of Huntington disease and cerebral atrophy

Ventricular sizes on computerized tomographic (CT) scans were compared in seven patients with Huntington disease, 20 patients with cerebral atrophy, and 20 normal controls. The bicaudate index—the ratio of the width of both lateral ventricles at the level of the heads of the caudate nuclei to the distance between the outer tables of the skull at the same level—significantly discriminated among the three groups. The bicaudate indices were: Huntington disease 0.209 ± 0.007, cerebral atrophy 0.121 ± 0.006, and controls 0.092 ± 0.003.

IMAGING OF ORBITAL LYMPHOPROLIFERATIVE DISORDERS

Lymphomas and leukemias account for a large portion of orbital tumors. Orbital lymphoma accounts for 55% of malignant orbital tumors in adults. Idiopathic orbital inflammatory pseudotumors are pathologic entities that often challenge ophthalmologists and radiologists. This article describes the MR and CT features of orbital lymphoma, leukemia, and some other lymphoproliferative disorders.

Middle Ear Masses Mimicking Glomus Tumors: Radiographic and Otoscopic Recognition

A high jugular bulb, an ectopic carotid artery, and an intratympanic cholesterol granuloma may, at times, mimic a middle ear glomus tumor, otoscopically. The otoscopic and radiographic findings which differentiate these lesions include microscopic otoscopy, tomography, carotid arteriography, and retrograde jugular venography. Examples of otoscopic and radiographic findings and procedures which enable the clinician to differentiate these lesions are presented.

Multidirectional and Computerized Tomography of the Vestibular Aqueduct in Meniere's Disease

Multidirectional and computerized tomography have been used for the radiographic assessment of the vestibular aqueduct in Menieres disease. The results of studies performed by us and or other authors indicate that there is a statistically significant difference in the size of the vestibular aqueduct between the Menieres and control groups (in Menieres disease the vestibular aqueduct is often narrowed or obliterated); and that periaqueductal pneumatization is often decreased or absent in ears affected by Menieres disease. Recent histological studies performed on temporal bones of patients with Menieres disease have confirmed these radiographic observations.

Further Studies on the Effects of Magnetic Resonance Imaging Fields on Middle Ear Implants

We investigated the effects of magnetic resonance imaging (MRI) fields on 21 stapedectomy prostheses and other middle ear implants and two different receiver-stimulator modules from 22-channel cochlear implants. None of the middle ear implants was displaced by the magnetic field, except for one platinum–stainless steel stapedectomy piston. Magnetism was not induced in any of the middle ear implants subjected to prolonged exposure in the MRI scanner. We conclude that MRI could pose a hazard to patients who have had stapedectomy using certain platinum–stainless steel piston prostheses and to patients with cochlear implants. Magnetic resonance imaging should pose no hazard to patients who have had the other middle ear implants reported on in this and our previous investigation.

Diagnosis of Retrocochlear and Central Vestibular Disease by Magnetic Resonance Imaging

Magnetic resonance imaging has become the study of choice for the diagnosis of retrocochlear and central vestibular disease. Three groups of lesions, each characterized by a specific site of origin, have been recognized: 1) petrous apex lesions such as congenital cholesteatomas and cholesterol granulomas involving the eighth cranial nerve within the internal auditory canal; 2) cerebellopontine angle tumors, mainly acoustic neuromas and meningiomas; and 3) CNS disease involving the brain stem and the central auditory and vestibular pathways such as tumors, multiple sclerosis, infarcts, and hemorrhage.

Inner Ear Fluid Volumes and the Resolving Power of Magnetic Resonance Imaging: Can it Differentiate Endolymphatic Structures?:

Magnetic resonance imaging (MRI) can accurately recognize minute volumes as small as 1 mm3. The volumes of the utricle and saccule of the inner ear are within the resolving power of MRI, but these structures cannot be recognized because the endolymph and perilymph signals are identical. To clarify the interpretation and description of inner ear structures on MRI, we measured and calculated the volumes of the perilymphatic and endolymphatic spaces of the human ear. We found the total volume of the bony labyrinth to be approximately 192.5 mm3 (endolymph, 34.0 mm3; perilymph, 158.5 mm3).

Predictability of magnetic resonance imaging in differentiation of orbital lymphoma from orbital inflammatory syndrome

Twenty-two patients with clinical presentations of either orbital lymphoma or orbital inflammatory syndrome (OIS) involving 25 orbits were examined by magnetic resonance imaging (MRI) before biopsy. To determine whether MRI adds specificity to radiographic diagnosis, the MRI signal characteristics of all tumors were examined. Attention was focused on the signal intensity of each tumor on T1- and T2-weighted images. In nine of 12 (75%) orbital lymphomas, the tumors appeared hyperintense to fat on T2-weighted images and became brighter relative to their appearance on T1-weighted images. In 11 of 13 (85%) orbital infiltrates with OIS, the tumors appeared isointense to fat on T2-weighted images and became slightly darker or unchanged relative to their appearance on T1-weighted images. Tumor density and homogeneity were fairly similar in all 25 lesions and were therefore not useful for further differentiation. Similarly, the presence of moderate enhancement with gadopentetate dimeglumine was seen in all but one tumor, and it was therefore not useful for further differentiation.