Occipital condyle screw fixation after posterior decompression for Chiari malformation: Technical report and application

Background: Surgical techniques for stabilization of the occipital cervical junction have traditionally consisted of screw-based techniques applied in conjunction with occipital plating and rods connected to subaxial instrumentation in the form of pars, pedicle, or lateral mass screws. In patients with type 1 Chiari malformation (CM-1) and evidence of occipital cervical junction instability who have undergone posterior decompression, the occipital condyle (OC) represents a potential alternative cranial fixation point. To date, this technique has only been described in pediatric case reports and morphometric cadaver studies. Methods: Patients underwent posterior fossa decompression for treatment of CM. Subsequently, patients received occipital cervical stabilization using OC screws. Results: Patients were successfully treated with no post-operative morbidity. Patient 2 was found to have pseudoarthrosis and underwent revision. Both patients continue to do well at 1-year follow-up. Conclusion: Placement of the OC screw offers advantages over traditional plate-based occipital fixation in that bone removal for suboccipital decompression is not compromised by the need for hardware placement, screws are hidden underneath ample soft tissue in patients with thin skin which prevents erosion, and the OC consists of primarily cortical bone which provides for robust tricortical fixation. These cases demonstrate the novel application of the OC screw fixation technique to the treatment of occipital cervical junction instability in adult patients undergoing simultaneous posterior fossa decompression.

Isolated traumatic occipital condyle fractures: Is external cervical orthosis even necessary?

Background: Occipital condyle fractures (OCFs) have been reported in up to 4–16% of individuals suffering cervical spine trauma. The current management of OCF fractures relies on a rigid cervical collar for 6 weeks or longer. Here, we calculated the rate of acute and delayed surgical intervention (occipitocervical fusion) for patients with isolated OCF who were managed with a cervical collar over a 10-year period at a single institution. Methods: This was a retrospective analysis performed on all patients admitted to a Level 1 Trauma Center between 2008 and 2018 who suffered traumatic isolated OCF managed with an external rigid cervical orthosis. Radiographic imaging was reviewed by several board-certified neuroradiologists. Demographic and clinical data were collected including need for occipitocervical fusion within 12 months after trauma. Results: The incidence of isolated OCF was 4% (60/1536) for those patients admitted with cervical spine fractures. They averaged 49 years of age, and 58% were male falls accounted for the mechanism of injury in 47% of patients. Classification of OCF was most commonly classified in 47% as type I Anderson and Montesano fractures. Of the 60 patients who suffered isolated OCF that was managed with external cervical orthosis, 0% required occipitocervical fusion within 12 months posttrauma. About 90% were discharged, while the remaining 10% sustained traumatic brain/orthopedic injury that limited an accurate neurological assessment. Conclusion: Here, we documented a 4% incidence of isolated OCF in our cervical trauma population, a rate which is comparable to that found in the literature year. Most notably, we documented a 0% incidence for requiring delayed occipital-cervical fusions.

The pattern of brain-size change in the early evolution of cetaceans

Most authors have identified two rapid increases in relative brain size (encephalization quotient, EQ) in cetacean evolution: first at the origin of the modern suborders (odontocetes and mysticetes) around the Eocene-Oligocene transition, and a second at the origin of the delphinoid odontocetes during the middle Miocene. We explore how methods used to estimate brain and body mass alter this perceived timing and rate of cetacean EQ evolution. We provide new data on modern mammals (mysticetes, odontocetes, and terrestrial artiodactyls) and show that brain mass and endocranial volume scale allometrically, and that endocranial volume is not a direct proxy for brain mass. We demonstrate that inconsistencies in the methods used to estimate body size across the Eocene-Oligocene boundary have caused a spurious pattern in earlier relative brain size studies. Instead, we employ a single method, using occipital condyle width as a skeletal proxy for body mass using a new dataset of extant cetaceans, to clarify this pattern. We suggest that cetacean relative brain size is most accurately portrayed using EQs based on the scaling coefficients as observed in the closely related terrestrial artiodactyls. Finally, we include additional data for an Eocene whale, raising the sample size of Eocene archaeocetes to seven. Our analysis of fossil cetacean EQ is different from previous works which had shown that a sudden increase in EQ coincided with the origin of odontocetes at the Eocene-Oligocene boundary. Instead, our data show that brain size increased at the origin of basilosaurids, 5 million years before the Eocene-Oligocene transition, and we do not observe a significant increase in relative brain size at the origin of odontocetes.

Trans-oral approach for occipital condyle biopsy: Case report and review of literature

Isolated occipital condyle lesions are commonly treated with empirical radiation, with the sole aim of relieving symptoms. Patients rarely undergo surgical biopsy, considering the morbidity associated with open surgery approaches and the importance of surrounding structures limiting the application of computed tomography (CT) scan or fluoroscopic percutaneous needle biopsies. We describe the case of a 66-year-old woman who was admitted on an emergency basis. Her clinical presentation included unilateral occipital headache and ipsilateral hypoglossal nerve palsy. Imaging revealed findings consistent with an isolated right occipital condyle lesion. In order to pursue a tissue diagnosis, essential to dictate medical management accurately, a minimally invasive biopsy of the occipital condyle through the trans-oral route was performed. Combined fluoroscopy, cone-bean CT and angiography allowed safe access to the lesion.

Hypoglossal Nerve Schwannoma With Severe Brainstem Compression: Microsurgical Excision by Extreme Lateral Approach: 2-Dimensional Operative Video

A 37-yr-old male presented with a history of left-sided tongue atrophy and fasciculations and weakness of upper limbs for 3 mo. Magnetic resonance imaging (MRI) revealed a large, partially cystic tumor with severe compression of the brainstem and spinal cord, with expansion and erosion of the hypoglossal canal. Computed tomography (CT) angiography showed the left vertebral artery to be anteriorly displaced by the tumor. A retrosigmoid craniotomy and craniectomy were performed followed by mastoidectomy with unroofing the posterior aspect of the sigmoid sinus. The foramen magnum was completely unroofed. The hypoglossal canal was exposed with a diamond drill and an ultrasonic bone curette, and a tumor was seen within the expanded canal. C1 lamina was removed partially in the lateral aspect, and the occipital condyle was partially removed. After opening the dura mater, the tumor was found to be stretching the eleventh cranial nerve. The tumor was debulked, and dissected from the cranial nerve fibers. The vertebral artery, anterior spinal artery, and other branches displaced by the tumor were carefully preserved. The tumor was removed from the hypoglossal canal with a curette. The patient recovered well, with the resolution of his upper limb weakness. Patient modified Rankin Scale was 1 at 6-mo follow-up. The postoperative MRI showed a small remnant inside the hypoglossal canal, and it was treated by radiosurgery. This 2-dimensional video demonstrates the technique of complete microsurgical removal of a complex tumor with preservation of cranial nerves and vertebral artery. Informed consent was obtained from the patient prior to the surgery, which included videotaping of the procedure and its distribution for educational purposes. Also, all relevant patient identifiers have been removed from the video and accompanying radiology slides.

An investigation of craniocervical stability post-condylectomy

Background: Occipital condylectomy is often necessary to gain surgical access to various neurological pathologies. As the lateral limit of the craniovertebral junction (CVJ), partial condylectomy can lead to iatrogenic craniocervical instability. What was once considered an inoperable location is now the target of various complex neurosurgical procedures such as tumor resection and aneurysm clipping. Methods: In this study, we will review the anatomical structure of the CVJ and provide the first comprehensive assessment of studies investigating craniovertebral stability following condylectomy with the transcondylar surgical approaches. Furthermore, we discuss future considerations that must be evaluated to optimize the chances of preserving craniocervical stability postcondylectomy. Results: The current findings postulate upward of 75% of the occipital condyle can be resected without significantly affecting mobility of the CVJ. The current findings have only examined overall dimensions and have not established a significant correlation into how the shape of the occipital condyles can affect mobility. Occipitocervical fusion should only be considered after 50% condyle resection. In terms of indicators of anatomical stability, components of range of motion (ROM) such as the neutral zone (NZ) and the elastic zone (EZ) have been discussed as potential measures of craniocervical mobility. These components differ by the sense that the NZ has little ligament tension, whereas the EZ does represent ROM where ligaments experience tension. NZ is a more sensitive indicator of instability when measuring for instability postcondylectomy. Conclusion: Various transcondylar approaches have been developed to access this region including extreme-lateral and far-lateral condylectomy, with hopes of preserving as much of the condyle as possible and maintaining postoperative craniocervical stability.

Evaluation of using the Anderson-Montesano and the Tuli classifications in pediatric patients with occipital condyle fractures

Background Occipital condyle fractures (OCFs) in patients before 18 years of age are rare. Classifications of OCF are based on the CT images of the cranio-cervical junction (CCJ) and MRI. The Anderson-Montesano and Tuli classifications are the types which are most commonly used in these cases. Classification of OCFs allows the implementation of OCF treatment. The aim of this study was to evaluate the effectiveness of using the OCF classification in pediatric patients based on the analysis of our own cases. Methods During the years 2013–2020, 6 pediatric patients with OCFs, aged 14–18, have been treated. Two patients with unstable fracture III according to Anderson-Montesano and IIB according to Tuli were treated with the halo-vest. Additionally, one patient presenting neurological symptoms and with an associated C1 fracture was qualified for the halo-vest stabilization as well. The other patients were treated with a Minerva collar. We evaluated the results 6 months after completing the OCF treatment using the Neck Disability Index (NDI) and SF-36 questionnaires. Confidence intervals for the mean values were verified using the MeanCI function (from the R library DescTools) for both classical and bootstrap methods. Results Based on NDI results, we have obtained in our patients an average of 4.33/45 points (2–11) and 9.62% (4.4–24.4). Based on the SF-36 questionnaire, we obtained an average of 88.62% (47.41–99.44). Conclusion The Anderson-Montesano and Tuli’s classifications of OCF can be used to assess the stability of OCF in adolescents, but both classifications should be used simultaneously. CT and MR imaging should be used in diagnosing OCFs, whereas CT allows assessing therapeutic outcomes in OCF.