Histopathology of idiopathic lateral skull base defects

Cerebrospinal Fluid Otorrhea After a Routine Tympanostomy Tube Placement: A Review of the Literature on Hyrtl Fissure

OBJECTIVE

To review the literature on Hyrtl fissure (HF) and contribute our experience with a 2-year old who developed cerebrospinal fluid (CSF) otorrhea during routine tympanostomy tube placement.

METHODS

Data Sources: Pubmed and Google Scholar searches were conducted of articles in the English language literature from all time periods using the words Hyrtl, Hyrtl's fissure, HF, and tympanomeningeal fissure. Study Selection: All relevant articles were reviewed to identify cases of HF.

RESULTS

Data Extraction: Nineteen cases, including ours, are described. Patient characteristics, method(s) of diagnosis and repair, and outcomes are reported. Computed tomography and intraoperative endoscopic images from our case are included. Presentation is more common in children (66.7% of cases where age was stated, n = 10) than in adults (33.3%, n = 5), and is most commonly unilateral (89.5%, n = 17). Cerebrospinal fluid otorrhea was the most common presentation. Six were discovered after tympanostomy tube placements while 3 were identified during cochlear implant work-up or after device failure. Surgical approaches described include endaural, transcanal, retrosigmoid, postauricular, and posterior fossa endoscopic. Multiple materials including bone wax, bone pate, fascia, muscle, and tissue sealant have been used. Our case describes an endoscopic repair in a child, which was successful at a 2-year follow-up. Data Synthesis: The small number of cases limits the utility of statistical analysis (n = 19).

CONCLUSIONS

Hyrtl fissure is a rare but important entity that may be discovered when routine procedures have unexpected results. Hyrtl fissure should be included in the differential diagnosis when there is persistent clear otorrhea after a tympanostomy tube, cochlear implant misinsertion, meningitis, or unexplained middle ear effusion in an adult.

Quantitative analysis of tegmen bone mineral density in obese and non-obese patients

BACKGROUND

Certain factors have been linked to lateral skull base demineralisation or erosion, which may predispose to spontaneous cerebrospinal fluid leak. There are relatively few quantitative reports of skull base changes in patient populations.

METHOD

A novel refined measurement algorithm for quantification of tegmen bone mineral density was developed, and bone mineral density between obese and non-obese patient groups was compared. Computed tomography scans were analysed by three blinded reviewers, and tegmen bone mineral densities were compared.

RESULTS

There were 23 patients in the obese group and 27 matched controls in the non-obese group. Inter-rater reliability was 'strong' to 'near complete' (κ = 0.75-0.86). No differences in tegmen bone mineral density were found between the groups (p = 0.64). The number of active blood pressure medications correlated positively with lateral skull base bone mineral density.

CONCLUSION

A novel, refined, quantitative measurement algorithm for the assessment of tegmen bone mineral density was developed and validated. Obesity was not found to significantly affect tegmen bone mineral density.

Petrous Apex Cephaloceles: Radiology Features and Surgical Management of a Rare Entity

OBJECTIVE

To characterize the radiologic findings of petrous apex cephalocele (PAC) in a patient cohort, and report the surgical management for three symptomatic PAC patients and cerebrospinal fluid (CSF) leak via the middle cranial fossa approach.

STUDY DESIGN

Retrospective case series.

SETTING

Academic center.

PATIENTS

Thirty-five patients with PAC were identified by review of the imaging archive between 2008 and 2019 (29 females; mean, 55 yrs; range, 4-86 yrs). All patients underwent magnetic resonance imaging of the skull base and/or computed tomography examination.

INTERVENTIONS

Surgical repair of PAC.

MAIN OUTCOME MEASURES

Radiologic features of PAC.

RESULTS

Radiological features of PAC: 25.7% bilateral; partial or expanded empty sella in 82.9%; arachnoid pits in 14.2%; and enlarged CSF space of optic nerve sheath in 20.0%. Coexisting pathology included temporal, sphenoid, and bilateral jugular foramen meningocele; as well as cribriform, middle crania fossa, and right temporal defect. Three case studies describing the surgical course of spontaneous CSF leak secondary to PAC were managed with the middle cranial fossa approach.

CONCLUSIONS

PAC is an exceedingly unusual cause for CSF leak in the adult and pediatric population. A middle fossa approach may be used to treat CSF leak as a result of PAC. Typically, CSF otorrhea originates from an encephalocele that extends via a bony defect in the tegmen tympani or tegmen mastoideum. However, on occasion the source of the CSF otorrhea is not via the tegmen, instead defects in the middle fossa floor, medial to the ridge for the gasserian ganglion (tubercle of Princeteau), need to be considered.

Peristapedial bulb: an indicator of spontaneous CSF leak in cochlear candidates with Mondini dysplasia

BACKGROUND

Mondini dysplasia with spontaneous cerebrospinal fluid (CSF) leak is rare in cochlear implantation (CI) candidates but lethal. Detailed evaluation and surgical intervention are needed for these patients.

AIM/OBJECTIVE

To report our findings of the peristapedial bulb in computer tomography (CT) as diagnostic evidence of spontaneous CSF leak and discuss its clinical value to direct the surgical plan for patients with profound sensorineural hearing loss (SNHL) and meningitis.

MATERIAL AND METHODS

A retrospective review was conducted, including patients' demographic features, radiographic examination, operation records, auditory/speech evaluation. The patients presented with a peristapedial bulb were included.

RESULTS

In 2775 CI recipients, 7 out of 219 (3.2%) patients with Mondini anomaly had detectable peristapedial bulbs in HRCT, among whom 6 patients have a history of meningitis. Surgical exploration verified the radiographic findings in 6 out of 7 patients. All patients received CI and vestibular obliteration. Control of meningitis was acceptable. The threshold of hearing significantly decreased from 74.1 dB ± 6.9 dB to 37.1 ± 4.8 dB after CI and the word recognition score elevated from 21.4 ± 14.9% to 78.6 ± 9.3%.

CONCLUSIONS AND SIGNIFICANCE

Peristapedial bulb is an indicator of spontaneous CSF leak in patients with profound SHNL and Mondini anomaly. Patients will benefit from CI and surgical intervention.

Spontaneous Congenital Perilabyrinthine Cerebrospinal Fluid Fistulas

OBJECTIVES

To report a recalcitrant spontaneous cerebrospinal fluid (CSF) fistula arising from multiple, anatomically-linked lateral skull base defects, and to review the available literature to determine optimal techniques for operative repair of congenital CSF fistulae.

METHODS

A patient with recurrent episodes of otologic meningitis was found to have a patent tympanomeningeal fissure, also known as a Hyrtl's fissure, and internal auditory canal (IAC) diverticulum that communicated with the jugular bulb. A systematic review of the literature characterized all reports of spontaneous congenital perilabyrinthine CSF leaks, and all cases of Hyrtl's fissures.

RESULTS

An 11-year-old female was referred for recurrent meningitis. Imaging demonstrated a fistulous connection between the middle ear and IAC diverticulum via the jugular foramen. Specifically, a Hyrtl's fissure was identified, as well as demineralized bone around the jugular bulb. Obliteration of the fissure was initially performed, and a fistula reformed 4 months later. Multifocal CSF egress in the hypotympanum was identified on re-exploration, and middle ear obliteration with external auditory canal (EAC) overclosure was performed. A systematic review of the literature demonstrated 19 cases of spontaneous congenital perilabyrinthine CSF leaks. In total, 6 cases had multiple sources of CSF leak and 2 had history suggestive of intracranial hypertension. All of these noted cases demonstrated leak recurrence. Middle ear obliteration with EAC overclosure was successful in 4 recalcitrant cases.

CONCLUSIONS

Repair of spontaneous congenital perilabyrinthine CSF leaks in cases demonstrating multiple sources of egress or signs of intracranial hypertension should be approached with caution. Middle ear obliteration with EAC overclosure may provide the most definitive management option for these patients, particularly if initial attempt at primary repair is unsuccessful.

Middle Cranial Fossa Repair of Temporal Bone Spontaneous CSF Leaks With Hydroxyapatite Bone Cement

OBJECTIVES

To determine the safety and effectiveness of the middle cranial fossa (MCF) approach in repairing spontaneous cerebrospinal fluid (sCSF) leaks.

STUDY DESIGN

Retrospective cohort study.

METHODS

Patient with sCSF leaks repaired by MCF approach between January 1, 2014 and August 31, 2019 were included. Demographic information, clinical and surgical findings, and postoperative outcomes were recorded.

RESULTS

The cohort (n = 45) included 24 tegmen repairs by multilayer reconstruction using hydroxyapatite cement and 21 cases of multilayer repair without hydroxyapatite cement. Ten MCF repairs were performed on patients ≥65 years old. Twenty (53%) ears had multiple tegmen defects (range, 1-9 tegmen defects) and 78% of patients had ≥1 encephaloceles. All sCSF leaks were resolved with one surgical intervention. There were no major intracranial complications. Transient expressive aphasia occurred in 2 patients. Medical complications occurred in four patients. There were no short-term postoperative CSF leaks with bone cement reconstruction and two postoperative leaks without bone cement. One resolved with lumbar drain (LD) and the other resolved without treatment. The average (SD) length of stay (LOS) with bone cement was shorter than in patients without bone cement (2.54 [0.83] days vs. 3.52 [1.99] days, P < .05). There have been no long-term CSF leak recurrences with an average (SD) follow-up of 13.5 (12.9) months (range 0.25-46 months).

CONCLUSIONS

MCF approach for sCSF repairs demonstrate efficacious outcomes, particularly with tegmen reconstruction using hydroxyapatite cement. The approach exhibited no serious adverse events and few complications requiring intervention. Therefore, MCF is a safe and effective approach to resolve sCSF leaks.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:624-632, 2021.

Prevalence of Spontaneous Asymptomatic Facial Nerve Canal Meningoceles: A Retrospective Review

BACKGROUND AND PURPOSE

The prevalence of patent facial nerve canals and meningoceles along the facial nerve course is unknown. This study aimed to assess the frequency of such findings in asymptomatic patients.

MATERIALS AND METHODS

A retrospective review was completed of patients with high-resolution MR imaging of the temporal bone whose clinical presentations were unrelated to facial nerve pathology. Facial nerve canals were assessed for the presence of fluid along each segment and meningoceles within either the labyrinthine segment (fluid-filled distention, ≥1.0-mm diameter) or geniculate ganglion fossa (fluid-filled distention, ≥2.0-mm diameter). If a meningocele was noted, images were assessed for signs of CSF leak.

RESULTS

Of 204 patients, 36 (17.6%) had fluid in the labyrinthine segment of the facial nerve canal and 40 (19.6%) had fluid in the geniculate ganglion fossa. Five (2.5%) had meningoceles of the geniculate ganglion fossa; no meningoceles of the labyrinthine segment of the canal were observed. No significant difference was observed in the ages of patients with fluid in the labyrinthine segment of the canal or geniculate ganglion compared with those without fluid (P = .177 and P = .896, respectively). Of the patients with a meningocele, one had a partially empty sella and none had imaging evidence of CSF leak or intracranial hypotension.

CONCLUSIONS

Fluid within the labyrinthine and geniculate segments of the facial nerve canal is relatively common. Geniculate ganglion meningoceles are also observed, though less frequently. Such findings should be considered of little clinical importance without radiologic evidence of CSF otorrhea, meningitis, or facial nerve palsy.

A Classification for the Anterior Inferior Cerebellar Artery-Subarcuate Artery Complex Based on the Embryological Development

Objective  To hierarchize the anterior inferior cerebellar artery (AICA)-subarcuate artery (SAA) complex's variations in the surgical field. Background  The AICA's "subarcuate loop" (SL) presents multiple variations, closely related to the SAA. AICA-SAA complex's variations may represent major issues in cerebellopontine angle (CPA) surgery. As the spectrum of configurations is originated during the development, a systematized classification was proposed based on the interaction between the petrosal bone and the AICA in the embryonic period. Methods  The variations were defined as follow: Grade 0: free, purely cisternal AICA, unidentifiable or absent SAA; Grade 1: purely cisternal AICA, loose SL, SAA > 3 mm; Grade 2: AICA near the subarcuate fossa, pronounced SL, SAA <3 mm; Grade 3: "duralized" AICA, unidentifiable SAA, or included in the petromastoid canal (PMC); and Grade 4: intraosseous AICA, unidentifiable SAA, or included in the PMC. The classification was applied to a series of patients assessed by magnetic resonance constructive interference in steady state sequence. Surgical examples were also provided. Results  Eighty-four patients were evaluated, including 161 CPA. The proportions found in the gradation remained within the range of previous publications (Grade 0: 42.2%; Grade 1: 11.2%; Grade 2: 35.4%; Grade 3: 10.6%; and Grade 4: 0.6%). Moreover, the degrees of the classification were related to the complexity of the anatomical relationships and, therefore, to the difficulty of the maneuvers required to overcome them. Conclusion  The proposed AICA-SAA complex classification allowed to distinguish and objectify pre- and intraoperatively the spectrum of variations, to thoroughly plan the required actions and instrumentation.

Giant Posterior Temporal Bone Arachnoid Granulations: CT and MRI Findings

OBJECTIVE

The radiologic appearance of arachnoid granulations (AGs) in typical locations is well established and they are rarely mistaken for other pathologies. However, when large and seen in atypical locations, such as along the posterior petrous bone, AGs can be a source of diagnostic and therapeutic confusion. We present two cases of giant posterior temporal bone AGs and review their clinical presentation, potential complications, and an imaging-based differential diagnosis.

PATIENTS

Two patients with surgically or pathologically proven giant symptomatic AGs in the posterior petrous bone.

MAIN OUTCOME MEASURE

Clinical presentation, radiological features, surgical findings, and potential complications of giant AGs.

RESULTS

In two middle-aged women (37 and 55 years), computed tomography (CT) demonstrated solitary large lytic lesions in the posterior right petrous temporal bone. These were similar in appearance to cerebrospinal fluid (CSF) on magnetic resonance imaging (MRI), though they exhibited some minor deviations such as thin internal septations, mild peripheral enhancement, and heterogeneous signal on fluid-attenuated inversion recovery (FLAIR). The MRI appearance effectively distinguished the giant AGs from other lesions that can occur in this area such as endolymphatic sac tumor (ELST). Surgery was successfully performed to prevent complications from a CSF leak.

CONCLUSION

The posterior temporal bone is an atypical location for AGs and can lead to diagnostic confusion, particularly when they are large. Familiarity with the characteristic imaging appearance of giant AGs in this location can help avoid misinterpretation as a more aggressive pathology and help recognize patients who are at risk for a CSF leak.

Posterior Fossa Spontaneous Cerebrospinal Fluid Leaks

OBJECTIVE

Describe the diagnosis and management of spontaneous lateral skull base cerebrospinal fluid (CSF) leaks that originate from the posterior fossa.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary university hospital.

PATIENTS

Adult patients from 2005 to 2015 who underwent surgical repair of a spontaneous lateral skull base CSF leak with intraoperative confirmation of a posterior fossa leak source.

INTERVENTION

Surgical repair.

MAIN OUTCOME MEASURES

CSF leak resolution.

RESULTS

Five patients had CSF leaks from the posterior fossa. The mean age at presentation was 54 years old (range, 19-79), the mean body mass index (BMI) was 32.6 (standard deviation [SD], 8.4), and the mean follow-up length was 34.6 months (SD, 19.4). Presentations did not differ from CSF leaks through middle fossa defects, including three patients with a history of meningitis and all patients with clear otorrhea following tympanostomy tube placement. All patients had resolution of the leak after surgical repair, but two patients required revision surgery for persistent leaks and one patient had a postoperative infection. Surgical approaches included one middle fossa, two transmastoid, one combined middle fossa/transmastoid, and one transcanal. Radiographic studies suggested a posterior fossa source in all cases but findings were often subtle.

CONCLUSION

Posterior fossa CSF leaks represent a rare subset of spontaneous lateral skull base leaks. Diligent radiographic review and intraoperative assessment of the posterior fossa plate are crucial. The size and location of the defect dictates the optimal surgical approach. Surgeons should consider a posterior fossa source in failed repairs or when the initial surgery did not fully evaluate the posterior fossa plate.