Syringomyelia intermittens: highlighting the complex pathophysiology of syringomyelia. Illustrative case

BACKGROUND Chiari Type I malformation (CM1) is a disorder recognized by caudal displacement of the cerebellar tonsils through the foramen magnum and into the cervical canal. Syringomyelia is frequently found in patients with CM1, but the pathophysiology of syringomyelia remains an enigma. As a general consensus, symptomatic patients should be treated and asymptomatic patients without a syrinx should not be treated. Mildly symptomatic patients or asymptomatic patients with a syrinx, on the other hand, pose a more challenging dilemma, as the natural evolution is uncertain. For many surgeons, the presence of a syrinx is an indication to offer surgery even if the patient is asymptomatic or mildly symptomatic. OBSERVATIONS The authors describe an illustrative case of a 31-year-old female with an incidental finding of a CM1 malformation and cervical syrinx in 2013. Conservative management was advocated as the patient was asymptomatic. Monitoring of the syrinx over a course of 8 years showed resolution, followed by reappearance and finally a complete resolution in 2021. A review of the literature and the possible pathophysiology is discussed. LESSONS The unusual course of this patient highlights the importance of guiding treatment by clinical symptoms, not radiological findings. Furthermore it reflects the complexity of the pathophysiology and the uncertain natural history of syringomyelia.

Functional and morphological changes in hypoplasic posterior fossa

Background The knowledge of the development and the anatomy of the posterior cranial fossa (PCF) is crucial to define the occurrence and the prognosis of diseases where the surface and/or the volume of PCF is reduced, as several forms of craniosynostosis or Chiari type I malformation (CIM). To understand the functional and morphological changes resulting from such a hypoplasia is mandatory for their correct management. The purpose of this article is to review the pertinent literature to provide an update on this topic. Methods The related and most recent literature addressing the issue of the changes in hypoplasic PCF has been reviewed with particular interest in the studies focusing on the PCF characteristics in craniosynostosis, CIM, and achondroplasia. Results and conclusions In craniosynostoses, namely, the syndromic ones, PCF shows different degrees of hypoplasia, according to the different pattern and timing of early suture fusion. Several factors concur to PCF hypoplasia and contribute to the resulting problems (CIM, hydrocephalus), as the fusion of the major and minor sutures of the lambdoid arch, the involvement of the basal synchondroses, and the occlusion of the jugular foramina. The combination of these factors explains the variety of the clinical and radiological phenotypes. In primary CIM, the matter is complicated by the evidence that, in spite of impaired PCF 2D measurements and theories on the mesodermal defect, the PCF volumetry is often comparable to healthy subjects. CIM is revealed by the overcrowding of the foramen magnum that is the result of a cranio-cerebral disproportion (altered PCF brain volume/PCF total volume). Sometimes, this disproportion is evident and can be demonstrated (basilar invagination, real PCF hypoplasia); sometimes, it is not. Some recent genetic observations would suggest that CIM is the result of an excessive growth of the neural tissue rather than a reduced growth of PCF bones. Finally, in achondroplasia, both macrocephaly and reduced 2D and 3D values of PCF occur. Some aspects of this disease remain partially obscure, as the rare incidence of hydrocephalus and syringomyelia and the common occurrence of asymptomatic upper cervical spinal cord damage. On the other hand, the low rate of CIM could be explained on the basis of the reduced area of the foramen magnum, which would prevent the hindbrain herniation.

Chiari Type I Malformation Presenting with Unilateral Hearing Loss

Introduction Chiari type I malformations can present in different ways, but the most frequent symptom is an occipitocervical headache. Hearing loss as the main presenting symptom is rare. Case A young woman with progressive left-sided unilateral hearing loss was diagnosed with a Chiari type I malformation. She underwent a suboccipital craniectomy with C1 laminectomy and duraplasty. The hearing loss had resolved postoperatively with normalization of the audiometry. Conclusion Chiari type I malformation can present solely with hearing loss. Improvement after surgical decompression is possible. This phenomenon is not emphasized well enough within the neurologic community. In this report, we present a summary of the pathophysiology and management in Chiari type I malformations.

Interscapular pain with Chiari Type I malformation attributed to atypical spinal accessory neuralgia

Background: The spinal accessory nerve (XI) is traditionally considered a motor nerve. However, as some studies have documented the presence of nociceptive fibers in XI, vascular XI neural compression may lead to an atypical neuralgia. Case Description: A 27-year-old male presented with a Chiari Type I malformation contributing to interscapular pain. Following a posterior fossa and microvascular decompression of XI, the patient improved, thus confirming the underlying diagnosis of a XI atypical neuralgia. Conclusion: Unilateral, posterior-interscapular deep pain may be due to an atypical spinal accessory nerve (XI) neuralgia rather than a Chiari Type I malformation or syrinx. Posterior fossa decompression, subpial tonsillar resection, and XI nerve microvascular decompression resolved this patient’s complaints. In the future, CTA or MRA vascular studies along with a balanced steady-state gradient echo MRI sequence would be better to document the presence of XI nerve neurovascular compromise.