ABSTRACT
Mammalian hearing depends on sound-evoked displacements of the stereocilia of inner hair cells (IHCs), which cause the endogenous mechanoelectrical transducer channels to conduct inward currents of cations including Ca2+. Due to their presumed lack of contacts with the overlaying tectorial membrane (TM), the putative stimulation mechanism for these stereocilia is by means of the viscous drag of the surrounding endolymph. However, despite numerous efforts to characterize the TM by electron microscopy and other techniques, the exact IHC stereocilia-TM relationship remains elusive. Here we show that Ca2+-rich filamentous structures, that we call Ca2+ ducts, connect the TM to the IHC stereocilia to enable mechanical stimulation by the TM while also ensuring the stereocilia access to TM Ca2+. Our results call for a reassessment of the stimulation mechanism for the IHC stereocilia and the TM role in hearing.
Subject(s)
Calcium/metabolism , Hair Cells, Auditory, Inner/physiology , Hearing/physiology , Stereocilia/physiology , Tectorial Membrane/physiology , Acoustic Stimulation , Animals , Female , Guinea Pigs , Male , Sound , Stereocilia/metabolism , Tectorial Membrane/anatomy & histology , Tectorial Membrane/diagnostic imagingABSTRACT
OBJECTIVE. A traumatic retroclival epidural hematoma is a rare imaging finding of severe cervical flexion-extension injury in the pediatric population. The purpose of our study was to identify pediatric patients with a retroclival epidural hematoma, record the hematoma size and extent, and examine the major craniocervical ligaments for injury. MATERIALS AND METHODS. Pediatric patients who suffered a retroclival epidural hematoma were identified retrospectively using the keywords "clivus," "epidural hematoma," and "retroclival" included in head CT reports between 2012 and 2019. The cervical and brain MRI examinations for these patients were reviewed for craniocervical ligament injury by two certified neuroradiologists. Detailed descriptions of patient injuries were recorded along with demographic information, clinical history, patient management, and outcome. RESULTS. Eleven pediatric patients were identified with an acute posttraumatic retroclival epidural hematoma with a mean anteroposterior dimension of 4.4 mm and craniocaudal dimension of 4.3 cm. All patients with a retroclival epidural hematoma who underwent subsequent cervical MRI had a stripping injury of the tectorial membrane (TM). Disruption of additional major craniocervical ligaments on MRI (alar ligament, transverse ligament, longitudinal ligaments, and ligamentum flavum) was relatively rare with the most common associated ligamentous injuries involving the anterior atlantooccipital membrane, apical ligament, and interspinous ligaments. None of the patients suffered a cervical cord or severe intracranial injury. The majority of the patients were managed conservatively with excellent clinical outcomes. CONCLUSION. A posttraumatic retroclival epidural hematoma in the pediatric population is a rare injury often identified initially by head CT and easily overlooked by the radiologist. We propose that a retroclival epidural hematoma in the pediatric population is a direct result of a significant flexion-extension force, with a subsequent stripping injury of the TM from the posterior clivus. Pediatric patients with a posttraumatic retroclival epidural hematoma on initial head CT should undergo a cervical MRI to evaluate the integrity of the TM and other craniocervical ligaments.
Subject(s)
Hematoma, Epidural, Cranial/diagnostic imaging , Magnetic Resonance Imaging/methods , Tectorial Membrane/diagnostic imaging , Tectorial Membrane/injuries , Adolescent , Child , Child, Preschool , Female , Humans , Male , Neuroimaging/methods , Retrospective StudiesABSTRACT
REHs and tectorial membrane injuries are rare complications of pediatric head and neck injuries. We aim to describe the neuroimaging findings in pediatric REHs, to summarize the mechanism of injury, and to correlate the imaging findings with the clinical presentation. We retrospectively evaluated CT and/or MR imaging studies of 10 children with traumatic REH. Most patients were involved in MVAs. The tectorial membrane was injured in 70% of patients, and REHs were medium to large in 80%. None of the patients had a focal spinal cord or brain stem injury, craniocervical junction dislocation, or vertebral fractures. Tectorial membrane disruption was diagnosed in most patients without craniocervical junction-related symptoms. Tectorial membrane lesions and REHs were seen in young children who sustained high-speed head and neck injuries. Clinical symptoms may be minimal or misleading. The radiologist should be aware of these injuries in children. MR imaging appears to be more sensitive than CT.
Subject(s)
Craniocerebral Trauma/complications , Craniocerebral Trauma/diagnosis , Magnetic Resonance Imaging , Tectorial Membrane/injuries , Tomography, X-Ray Computed , Adolescent , Child , Child, Preschool , Diagnosis, Differential , Female , Humans , Infant , Reproducibility of Results , Sensitivity and Specificity , Subtraction Technique , Tectorial Membrane/diagnostic imaging , Tectorial Membrane/pathologyABSTRACT
An 11-year-old girl presented with a very rare traumatic retroclival epidural hematoma manifesting as bilateral abducens nerve palsy, deviation of the uvula to the left, and weakened movement of tongue, which developed after a motor vehicle accident. The patient was treated conservatively and showed good outcome. Retroclival hematoma is a mainly pediatric entity usually associated with ligamentous injury at the craniocervical junction, and can be treated conservatively with good outcome.
