Chiari I malformation associated with atlanto-occipital assimilation presenting as orthopnea and cough syncope

Human genetics and molecular genomics of Chiari malformation type 1

Chiari malformation type 1 (CM1) is the most common structural brain disorder involving the craniocervical junction, characterized by caudal displacement of the cerebellar tonsils below the foramen magnum into the spinal canal. Despite the heterogeneity of CM1, its poorly understood patho-etiology has led to a 'one-size-fits-all' surgical approach, with predictably high rates of morbidity and treatment failure. In this review we present multiplex CM1 families, associated Mendelian syndromes, and candidate genes from recent whole exome sequencing (WES) and other genetic studies that suggest a significant genetic contribution from inherited and de novo germline variants impacting transcription regulation, craniovertebral osteogenesis, and embryonic developmental signaling. We suggest that more extensive WES may identify clinically relevant, genetically defined CM1 subtypes distinguished by unique neuroradiographic and neurophysiological endophenotypes.

Cough syncope and hyperventilation-induced convulsion in Chiari 1.5 malformation

Chiari malformation type I (CM1) is defined as cerebellar tonsillar herniation below the level of the foramen magnum. Syncope, especially cough syncope, is a rare but important symptom of CM1 patients. Here, we report a CM1 patient, in combination with brainstem herniation (CM1.5), presenting with repetitive syncope who was successfully treated by decompressive surgery. A 43-year-old right-handed male, with 5-year history of repeated episodes of loss of consciousness in association with cough, was investigated. Neurological examination revealed slight muscle weakness, clumsiness, and sensory disturbance in the left upper limb. There was no sign of orthostatic hypotension or orthostatic intolerance. Cranial and spinal magnetic resonance imaging revealed a herniation of the cerebellar tonsils and a syringomyelia. Forced hyperventilation during electroencephalogram (EEG) induced brief generalized symmetric clonic convulsions with preserved consciousness, but no overt EEG seizure patterns or slow activities were found. Based on the diagnosis of CM1.5 with recurrent episodes of loss of consciousness, he underwent foramen magnum decompression. He has no recurrence of the episode after the surgery on 1 year follow-up. Decompressive surgery was an effective procedure for cough syncope and other symptoms of the current patient with CM1.5. Dissociation of cerebrospinal fluid pressure between the cranial and spinal compartments which leads further herniation of the cerebellar tonsils and subsequent compression on the cerebellum and the brainstem is considered to be the major mechanism of his cough syncope. Analysis of EEG can be useful not only to diagnose epileptic seizures but also to elucidate mechanisms of syncope and concurrent involuntary movements.

Chiari Malformation Type 1: A Systematic Review of Natural History and Conservative Management

BACKGROUND

Chiari malformation type 1 (CM-1) is a variation of hindbrain development that can sometimes occur in asymptomatic individuals. Conventional treatment is surgical decompression, but little is known about the natural history of patients who do not undergo surgical management. This information is critical to determine how these patients should be managed. We conducted a systematic literature review to determine the natural history of CM-1, particularly in patients who did not undergo surgery and in asymptomatic individuals, to help patients and physicians determine when surgery is likely to be beneficial.

METHODS

The literature search was performed following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines using the electronic databases PubMed, Scopus, Cochrane Library, and Web of Science. Inclusion and exclusion criteria were predefined.

RESULTS

In symptomatic patients who did not undergo surgery, headaches and nausea often improved, whereas ataxia and sensory disturbance tended not to improve spontaneously. Of patients, 27%-47% had an improvement in symptoms after 15 months, and 37%-40% with cough headache and 89% with nausea who were managed nonoperatively improved at follow-up. Most asymptomatic individuals with CM-1 remained asymptomatic (93.3%) even in the presence of syringomyelia.

CONCLUSIONS

The natural history of mild symptomatic and asymptomatic CM-1 in adults is relatively benign and nonprogressive; the decision to perform surgical decompression should be based on severity and duration of a patient's symptoms at presentation. It is reasonable to observe a patient with mild or asymptomatic symptoms even in the presence of significant tonsillar descent or syringomyelia.

Type I Chiari malformation presenting orthostatic syncope who treated with decompressive surgery

Chiari malformations are a congenital anomaly of the hindbrain. The most common, Chiari malformation type I (CM-I), is characterized by herniation of the cerebellar tonsils extending at least 3 mm below the plane of the foramen magnum. Consequently, CM-I is associated with hydrocephalus and symptoms involving compression of the cervicomedullary junction by ectopic tonsils. Several studies have reported the clinical symptoms associated with CM-I, including suboccipital headache, weakness in the upper extremities, facial numbness, loss of temperature sensation, ataxia, diplopia, dysarthria, dysphagia, vomiting, vertigo, nystagmus, and tinnitus. Syncope is one of the rarest presentations in patients with CM-I. There are many hypotheses regarding the causes of syncope in patients with CM-I; however, the mechanisms are not clearly understood. Although surgical decompression for CM-I in patients with syncope has yielded good clinical results in some studies, such cases are rarely reported. We report a case of orthostatic syncope in a patient with CM-I who was treated with surgical intervention.