Langerhans Cell Histiocytosis of the Temporal Bone with Otic Capsule Involvement.

INTRODUCTION: This study is conducted to demonstrate that destructive lesions of the otic capsule by Langerhans cell histiocytosis (LCH) causing both radiographic and audiologic findings can be completely reversed with adequate treatment. Retrospective case review and analysis of clinical and imaging data were obtained as part of the diagnosis and treatment of patients with LCH of the temporal bone. METHODS: With Institutional Review Board (IRB) approval, cases of LCH involving the temporal bone were searched for within the institutional databases. Criteria for inclusion was histologic diagnosis of LCH and pretreatment computed tomography (CT) demonstrating temporal bone and/or otic capsule involvement and posttreatment follow-up CT/magnetic resonance imaging (MRI) scans obtained at least 6 months after starting treatment. RESULTS: We report eight cases of LCH of the temporal bone with three demonstrating otic capsule involvement radiographically and/or clinically. Review of posttreatment imaging revealed all three patients had complete restoration of the bony labyrinthine architecture and near or complete restoration of their hearing. CONCLUSIONS: Though LCH of the temporal bone is a common site within the spectrum of the disease, involvement of the otic capsule remains rare. Here, we report the largest series of otic capsule involvement by LCH and investigate whether both architecture and hearing are recovered with appropriate treatment. Lastly, restoration of the bony architecture of the labyrinth suggests the mechanism of LCH is demineralization and not ablative.

Sphenoethmoid cerebrospinal fluid leak repair with hydroxyapatite cement.

Despite advances in neurological, reconstructive, and endoscopic sinus surgery, sphenoethmoid cerebrospinal fluid (CSF) fistulae continually pose difficult management problems. Standard surgical techniques for fistulae closure succeed approximately 78% to 90% of the time. To improve this success rate, hydroxyapatite cement (HAC), a Food and Drug Administration-approved substance for cranial defect repair, was applied to this problem in a clinical setting. Twenty-one patients with spontaneous, posttraumatic, or postoperative CSF leaks of the sphenoid sinus, cribriform plate, or ethmoid region were treated with HAC. Study participants were prospectively accrued at 5 tertiary care medical centers in the eastern United States. The CSF leaks of all 21 patients treated with HAC were successfully sealed by its initial application. The sites of CSF leakage included the nasal cavity (n = 2) and sphenoid sinus (n = 19). Fifteen of the patients had previously undergone a failed repair by standard methods. There have been no recurrent CSF leaks with a maximum follow-up of 72 months, and an average follow-up of 36 months. All patients have survived to date. The only HAC-related morbidity was the extrusion of the HAC when placed in the nasal cavity. Hydroxyapatite cement is an effective method of repair for postoperative, posttraumatic, and spontaneous sphenoid CSF leaks. The efficacy of HAC in sealing the CSF leak was unaffected by previous attempts at leak closure by standard methods or by its origin. Hydroxyapatite cement should not be applied transnasally for the treatment of an ethmoid region fistula owing to its high probability of extrusion. Correct patient selection and technical familiarity with HAC are necessary for successful application.

Elimination of temporal bone cerebrospinal fluid otorrhea using hydroxyapatite cement.

OBJECTIVE: This report introduces a new method to control cerebrospinal fluid (CSF) otorrhea using hydroxyapatite cement (HAC) via a transmastoid approach. This technique eliminates the need for a transmastoid or middle cranial fossa approach with soft tissue repair and prolonged hospitalization caused by lumbar drainage. STUDY DESIGN: Retrospective review. METHODS: Thirteen cases of transmastoid repairs of CSF otorrhea using HAC from August 1996 to February 1999 were reviewed. RESULTS: The CSF leak was controlled in every patient using HAC through a transmastoid approach. The reconstruction involved eight tegmen defects, three posterior fossa dural plate defects, and two congenital inner ear fistula secondary to Mondini malformation. Postoperative wound infection in one patient was the only complication that occurred. The average hospital stay was 48 hours. Follow-up ranged from 12 to 44 months with no recurrence of CSF otorrhea. CONCLUSION: The successful use of HAC to control CSF otorrhea through a transmastoid approach reduces patient morbidity by obviating the need for middle cranial fossa approaches, donor soft tissue sites, and spinal drainage.

Comparison of optokinetic nystagmus elicited by full versus partial visual field stimulation: diagnostic implications.

Optokinetic nystagmus (OKN) testing is one method to determine central vestibular dysfunction. OKN may be elicited by partial visual field stimulation with a light bar (OKN-ENG) or by full visual field stimulation with rotating stripes in a rotational chair test booth (OKN-RVT). OKN-ENG and OKN-RVT were elicited in 36 healthy subjects and 48 patients with known peripheral or central vestibular disorders. Abnormal test results suggested central pathology in 29 of 36 healthy subjects with OKN-ENG versus 1 of 36 with OKN-RVT. Twenty-eight of 33 patients with peripheral pathology demonstrated abnormal OKN-ENG findings, whereas 4 of 33 had abnormal OKN-RVT results. Thirteen of 15 patients with central vestibular disorders had abnormal OKN-ENG, whereas 7 of 15 had abnormal OKN-RVT. Sensitivity and specificity of OKN-ENG were 86.7% and 17.4% versus 46.7% and 92.7%, respectively, for OKN-RVT. These findings were statistically significant (P < 0.00001). OKN elicited by full visual field stimulation (OKN-RVT) is a more accurate indicator of central disease than OKN elicited by partial visual field stimulation (OKN-ENG). The use of OKN-ENG to identify central vestibular dysfunction is questionable.

Anesthesia of the chorda tympani nerve and taste phantoms.

The chorda tympani nerve innervates the anterior two-thirds and the glossopharyngeal nerve, the posterior one-third, of each side of the tongue. Previous work showed that anesthesia of one chorda tympani increased the perceived intensity of quinine applied to an area innervated by the contralateral glossopharyngeal nerve, but decreased the perceived intensity of NaCl applied to an area innervated by the ipsilateral glossopharyngeal nerve. The data presented here corroborate that earlier finding and show that if both chorda tympani nerves are anesthetized, the taste of quinine is intensified and the taste of NaCl diminished at areas innervated by the glossopharyngeal on both sides of the tongue. In about 40% of the subjects, tastes occurred in the absence of stimulation (we call these tastes phantoms). The phantoms were usually localized to the posterior tongue contralateral to the anesthesia and they were abolished when a topical anesthetic was applied to the area where they were perceived. Phantoms like these may be a source of clinical dysgeusia in patients with localized taste damage. The phantoms may result because the anesthesia releases inhibition normally occurring between the central projection areas of different taste nerves.

Obliteration of the eustachian tube using hydroxyapatite cement: a permanent technique.

Permanent obliteration of the eustachian tube via the middle ear traditionally has met with limited success. Combinations of muscle, fascia, adipose tissue, bone fragments, and inert material such as Proplast have been used to seal the middle ear from the nasopharynx by inciting a fibrous reaction within the lumen of the eustachian tube. Long-term follow-up has demonstrated repneumatization of the middle ear cleft in the majority of cases, indicating failure of the obliteration technique. This report describes a technique for successful long-term obliteration using hydroxyapatite cement. This new biomaterial possesses osseointegrative and osseoconductive properties that result in permanent obliteration by producing new bone formation within the lumen of the eustachian tube. This technique eliminates the complication of cerebrospinal fluid rhinorrhea in lateral skull base procedures that expose the eustachian tube to cerebrospinal fluid.

Indications for hydroxyapatite cement reconstruction in lateral skull base surgery.

Preliminary data on the use of hydroxyapatite cement to restore cranial bone integrity has shown excellent results. Cranial base reconstruction has been accomplished for translabyrinthine, middle cranial fossa, and suboccipital craniectomy defects, as well as extensive temporal bone fractures. Fifteen patients have been followed for up to 2 years with no evidence of complication from use of the hydroxyapatite cement. Exposure to cerebrospinal fluid does not appear to alter its stability, and pre-existing infection appears to be the only contraindication to its use. Stability of the cement has been confirmed by serial radiographic analyses. This paper reviews the chemical structure and bioactivity of hydroxyapatite cement and employs case studies to illustrate the applications of this new biomaterial in lateral skull base surgery.

Effect of anesthesia of the chorda tympani nerve on taste perception in humans.

Individuals who have sustained considerable damage to parts of the taste system often fail to experience changes in everyday taste experience. The two halves of the tongue are independently innervated: the chorda tympani (branch of the facial or VIIth cranial nerve) innervating the anterior two-thirds and the glossopharyngeal (IXth cranial nerve) innervating the posterior one-third. Anesthesia of the chorda tympani nerve on one side produced increased taste intensities for some stimuli on the area innervated by the glossopharyngeal nerve on the other side. Because this effect occurs across the midline and taste projects ipsilaterally, the effect must occur in the central nervous system (CNS). This supports Halpern and Nelson's release-of-inhibition hypothesis that the area to which the chorda tympani projects in the CNS must normally inhibit that of the glossopharyngeal nerve. Anesthesia of the chorda tympani abolishes that inhibition and leads to perception of increased taste intensities from areas innervated by the glossopharyngeal nerve.

Reconstruction of suboccipital craniectomy defects with hydroxyapatite cement: a preliminary report.

Hydroxyapatite cement, a new biomaterial presently under clinical investigation, has been demonstrated to have potentially wide application in cranial reconstruction. We describe our experience with this biologic bone cement in the reconstruction of suboccipital craniectomy defects in seven patients after vestibular schwannoma removal. With up to 2-year follow-up, cranial bone integrity has been reestablished in five patients. Dissolution of cement has occurred in dependent areas and appears to be technique related. Cranial bone contour appears dependent on the amount of cement used. The frequency of debilitating postoperative headache was reduced in these patients when compared to patients who had no reconstruction of the craniectomy defect. Reconstruction of the bony defect after suboccipital craniectomy with hydroxyapatite cement is not only useful to restore cranial contour, but also appears to reduce some of the functional deficits attributed to this surgical approach.

Particulate matter within the membranous labyrinth: pathologic or normal?

Recent reports have suggested that particulate matter identified within the membranous portion of the posterior semicircular canal is responsible for the development of positional vertigo. To further investigate this claim, a posterior canal fenestration was carried out in ten patients undergoing acoustic tumor removal via a translabyrinthine approach. Particles were identified in the membranous labyrinth in nine patients. One of these patients described positional vertigo preoperatively. Electron microscopy demonstrated particles within the membranous labyrinth that appeared to be of mixed proteinaceous and mineral content. These data suggest that further studies must be undertaken before the theory of endolymphatic particle migration can be confirmed as the etiology of positional vertigo.

The effect of unilateral chorda tympani damage on taste.

Patients with localized damage to the taste system often experience no subjective change in real-world taste experience. In an effort to understand this, eight patients who recently underwent acoustic neuroma removal were evaluated for taste loss. Localized taste testing showed that taste intensities decreased in the distribution of cranial nerve VII ipsilateral to tumor removal as expected, but asymmetries occurred for IX. Intensities were greater on the side contralateral to the tumor removal. In addition, palatal taste, also thought to be mediated by VII, was not totally abolished. It is concluded that cranial nerve IX is normally inhibited by cranial nerve VII in the taste network. When VII is damaged, this inhibition is abolished. This release of inhibition serves as a compensation mechanism that preserves normal taste experience.

Referred otalgia.

Referred otalgia is a challenging symptom, with the burden on the physician to identify the source. Only by careful patient history and physical examination can all causes in this extensive differential diagnosis be excluded. In the absence of primary otologic pathology, referred pain from a head and neck carcinoma must be considered foremost and ruled out.

Transtemporal approaches to the skull base.

Transtemporal approaches to lesions of the posterior fossa and/or temporal bone afford direct access with minimal manipulation of the subdural spaces. In most instances, the primary concern is the preservation of seventh nerve integrity or restoration of seventh nerve function in the event of loss of facial nerve integrity. The transtemporal approaches afford the surgeon the ability to trace the seventh nerve from normal to diseased regions and so increased the possibility of anatomical preservation. In addition, the availability of the seventh nerve for transposition or rerouting makes nerve grafting easier in the event of seventh nerve sacrifice. Limitation of the craniectomy site within the temporal bone without violating the deep cervical musculature avoids the complication of severe postoperative headaches so frequently seen in suboccipital resections. Thorough knowledge of the temporal bone anatomy and intracranial structures is mandatory prior to utilization of this procedure.

The efficacy of brainstem auditory evoked potentials in acoustic tumor surgery.

As the identification of patients with small acoustic neuromas and salvageable hearing increases, intraoperative auditory nerve monitoring has been used increasingly in an attempt to improve the hearing preservation rate. Far-field recordings obtained by brainstem auditory evoked potentials (BAEP), at times enhanced by electrocochleography, have become a standard method of intraoperative auditory nerve assessment. To evaluate the usefulness of this monitoring technique, the hearing preservation results of a series of unmonitored acoustic tumor removals were compared to a series of patients monitored via the standard brainstem auditory evoked potentials. With comparable average tumor sizes, 4 of 7 unmonitored patients had hearing preserved at preoperative levels compared to 4 of 9 monitored patients. Neither preoperative BAEP assessments nor absolute tumor size were predictive of hearing preservation. This report brings into question the effectiveness of far-field intraoperative BAEP monitoring during acoustic tumor resection and suggests that direct auditory nerve monitoring may be more appropriate.

Delayed spontaneous return of hearing after acoustic tumor surgery: evidence for cochlear nerve conduction block.

Unlike the eventual resolution of facial paralysis in most patients with intact facial nerves, delayed hearing return after acoustic tumor resection is rare. This discrepancy in recovery has been ascribed to the inherent resilience of the facial nerve (a special visceral efferent nerve) to injury versus the cochlear nerve (a special somatic afferent nerve). In the presence of an intact cochlear nerve, hearing loss has been attributed to transection or spasm of the internal auditory artery or to direct mechanical trauma to the cochlear nerve during manipulation of the tumor. The possibility of a reversible conduction block in the cochlear nerve has not been considered. A review of three instances of delayed spontaneous hearing recovery several months after acoustic tumor resection suggests that a conduction block phenomenon can exist. This report describes the pathophysiology and the possible intraoperative predisposing features of this condition.

Correlation of high resolution computed tomography and gross anatomic sections of the temporal bone. Part III. Cochlear and vestibular aqueducts.

Gross anatomic sections of isolated temporal bones (TB) were compared with high resolution computed tomography (CT) scans obtained utilizing contiguous 1.5-mm thick slices in the transaxial, coronal, and sagittal planes. Each TB was then sectioned at 2.0-mm intervals in planes parallel to those of the CT scans. Both the cochlear and vestibular aqueducts were best visualized in the coronal plane; the transaxial plane proved less reliable and the sagittal plane was not useful at all. The cochlear aqueduct in the coronal plane appears as a funnel-shaped configuration with its widest portion opening into the subarachnoid space. The vestibular aqueduct at its opening into the epidural space is well visualized in the coronal plane, and as it traverses the bone toward the vestibule it appears as an oval to spherical lucency, whereas in transaxial sections it is seen as a small longitudinal lucency.

Cochlear nerve conduction block: an explanation for spontaneous hearing return after acoustic tumor surgery.

In the presence of an intact cochlear nerve, hearing loss has been attributed to either transection or spasm of the internal auditory artery or direct mechanical trauma to the cochlear nerve during tumor manipulation. Such events have been correlated with changes in intraoperative auditory evoked potentials. The possibility of a reversible conduction block in the cochlear nerve, however, has not been investigated. Review of four cases of delayed spontaneous recovery of hearing several months after acoustic tumor resection suggests that a conduction block phenomenon may exist. By comparing recent pertinent animal data with clinical intraoperative electrophysiologic data obtained during posterior fossa surgery in human subjects, we attempt to elucidate further the pathophysiology and intraoperative predisposing factors to cochlear nerve injury during hearing preservation procedures.

Cochlear implantation after transmastoid labyrinthectomy.

Hearing rehabilitation with an intracochlear prosthesis is well documented in patients who have an intact otic capsule prior to implantation. However, the suitability for implantation of patients who have undergone extensive procedures involving the otic capsule such as labyrinthectomy has not been directly addressed. This report documents a case of a patient deafened by a transmastoid labyrinthectomy who subsequently received a cochlear implant. Postimplantation performance of this patient was compared with the performance of three other postlingual implant recipients. The results suggest that labyrinthectomy is not a contraindication to auditory rehabilitation by a cochlear implant. The implications of implantation in a surgically manipulated otic capsule are discussed.