La malformation de Chiari de type 1 à l’ère de l’imagerie par résonance magnétique

MRI Insights in Chiari Malformation Type 1 and Variations With Hydrosyringomyelia

Chiari malformation (CM) type 1 is a complex neurological disorder characterized by the displacement of the cerebellar tonsils into the upper spinal canal. Hydrosyringomyelia (HSM), which frequently coexists with this condition, presents diagnostic and treatment problems due to its broad spectrum of symptoms. There are various forms of CMs, with CM type 1 (CM1) being the most common type. Magnetic resonance imaging (MRI) is the best imaging technique to properly identify and diagnose CM1 and HSM. Important imaging findings include downward displacement of the cerebellar tonsils across the foramen magnum, the appearance of the syrinx in the spinal cord, and the alteration of the flow dynamics of the cerebrospinal fluid. This study was conducted at Datta Meghe Medical College, Nagpur, and Government Medical College & Super Speciality Hospital, Nagpur, India. It focuses on the diagnostic use of MRI in CM1 and its variations associated with HSM. Individuals who are asymptomatic may not need any treatment; however, those who are symptomatic or have HSM may require surgical decompression and restoration of the flow. We discuss the findings of MRI of six cases of CM1 and its variants with HSM and search for possible underlying causes. We conclude that magnetic resonance imaging is an imaging modality for the identification and evaluation of CM1 in cases of HSM.

Effect of Body Mass Index on Chiari Malformation 1 Tonsil Ectopia Length in Adults

OBJECTIVE

Diagnosis of Chiari I malformation (CM-1) is based on measurements of the inferior extension of the cerebellar tonsils into the foramen magnum on cranial or cervical spine magnetic resonance imaging. Imaging may be obtained before the patient is referred to the neurosurgical specialist. The length of time raises questions about the possibility that body mass index (BMI) fluctuations could affect the measurement of ectopia length. However, previous literature on BMI and CM-1 has reported conflicting findings on BMI.

METHODS

We conducted a retrospective chart review of 161 patients who were referred to a single neurosurgeon for CM-1 consultation. Patients with multiple recorded BMI values (n = 71) were compared to see if BMI changes correlated with changes in ectopia length. In addition, we compared and tested 154 recorded ectopia lengths from the patients (1 per patient) and patient BMI values with Pearson correlation and Welch t tests to determine if BMI changes either influenced or were associated with ectopia changes.

RESULTS

For the 71 patients with multiple BMI values, change in ectopia length ranged from -4.6-9.8 mm but was not statistically significant (r = 0.019; P = 0.88). For the 154 measured ectopia lengths, changes in BMI did not correlate with ectopia length (P > 0.05). Likewise, differences in ectopia length between patients in normal, overweight, and obese categories were not statistically significant (|tstat| < |tcrit|, P > 0.05).

CONCLUSIONS

In individual patients, we found that BMI and changes in BMI were not accompanied by changes in tonsil ectopia length.

Cranial Versus Cervical Spine Magnetic Resonance Imaging in Adult Chiari Malformation Type I Diagnostics: Is There a Difference in Tonsil Ectopia Length?

BACKGROUND

Chiari malformation type 1 (CM-1) diagnosis is based on measurement of the cerebellar tonsils on cranial or cervical spine magnetic resonance imaging (MRI). However, imaging parameters of cranial and cervical spine MRI could differ because spine MRI has greater resolution.

METHODS

We conducted a retrospective chart review of 161 patients of a single neurosurgeon for adult CM-I consultation between February 2006 and March 2019. Patients were selected based on receiving both cranial and cervical spine MRI within a month of each other to determine tonsillar ectopia length for CM-1. Ectopias were measured to determine if differences in values were statistically significant.

RESULTS

From the 161 total patients, 81 had cranial and cervical spine MRI for a total of 162 tonsil ectopia measurements (81 cranial and 81 spinal). Average ectopia length on a cranial MRI was 9.1 mm (±5.2 mm); average ectopia length on a spinal MRI was 8.9 mm (±5.3 mm). Average cranial and spinal MRI values were found to be <1 standard deviation apart. Two-tailed, nonequal variances t test determined that differences between the cranial and spinal ectopia measurements were insignificant (P = 0.2403).

CONCLUSIONS

This study confirmed that the added resolution offered by spine MRI did not make better or more refined measurements over cranial MRI that could lead to measurement differences, which can instead be attributed to chance. Cranial and cervical spine MRI can be used to determine the degree of the tonsil ectopia.

Chiari-like Malformation

Chiari-like malformation is a condition of the craniocervical junction in which there is a mismatch of the structures of the caudal cranial fossa causing the cerebellum to herniate into the foramen magnum. This herniation can lead to fluid buildup in the spinal cord, also known as syringomyelia. Pain is the most common clinical sign followed by scratching. Other neurologic signs noted are facial nerve deficits, seizures, vestibular syndrome, ataxia, menace deficit, proprioceptive deficits, head tremor, temporal muscle atrophy, and multifocal central nervous system signs. MRI is the diagnostic of choice, but computed tomography can also be used.

Obstructive sleep apnoea associated with syringomyelia

Coexistence of obstructive sleep apnoea and syringomyelia is quite rare. This article discusses three cases of coexisting obstructive sleep apnoea and syringomyelia and looks at the possible mutual influences between the two diseases.

Chiari 1 malformation and holocord syringomyelia in hunter syndrome

Compressive cervical myelopathy is a well-known life-threatening complication in mucopolysaccharidosis (MPS) patients. Glycosaminoglycan accumulation in the growing cartilage results in dens dysplasia, atlanto-axial instability, and subsequent periodontoid fibrocartilaginous tissue deposition with upper cervical stenosis.Chiari malformation type 1 (CM1) is a congenital downward cerebellar tonsil ectopia determined by clivus and posterior cranial fossa underdevelopment, possibly leading to progressive spinal cord cavitation (syringomyelia) and severe neurological impairment.We present a boy affected with Hunter syndrome (MPS II) and cerebellar tonsil ectopia who developed a holocord syringomyelia at the age of 6 years. The child underwent atlanto-occipital decompressive surgery with rapid clinical and neuroimaging improvement.Sharing a primary mesenchymal involvement of the cervical-occipital region, the coexistence of CM1 in MPS might be not unexpected and complicate further the disease course. In these patients, strict monitoring and prompt treatment might be of foremost importance for preventing major neurological complications.

Resolution of life-threatening dysphagia caused by caudal occipital malformation syndrome following foramen magnum decompressive surgery

A Cavalier King Charles Spaniel was presented with acute onset, life-threatening dysphagia suspected to be secondary to medulla oblongata compression caused by caudal occipital malformation syndrome. The patient required urgent tracheostomy tube placement to remain stable and was subsequently cured of the presenting neurological deficits by foramen magnum decompressive surgery. Neurogenic dysphagia is a relatively common presenting sign in human Chiari malformation syndromes, but has not been described as a major clinical sign in veterinary patients. Caudal occipital malformation syndrome should be included in the differential diagnosis list for susceptible breeds presenting with dysphagia. Early recognition favours expeditious surgical intervention and a positive outcome in human patients, and this may also be the case in veterinary patients.

[Hemihypertrophy and scoliosis revealing a Chiari 1 malformation with syringomyelia]

We report the case of a 9-year-old boy with progressive thoracic scoliosis and crossed hemihypertrophy who was discovered with a Chiari 1 malformation and syringomyelia. These disorders are connected by complex physiopathological mechanisms; their association deserves attention. This observation reviews the importance of the clinical examination, particularly the neurological exam, in childhood scoliosis. The features suggesting a neurogenic background of spine deformation should be sought. Scoliosis with hemihypertrophy can be the sign of an underlying neurological abnormality.

Arnold-Chiari malformation type 1 complicated by sudden onset anterior spinal artery thrombosis, tetraparesis and respiratory arrest

Chiari in 1891 described a constellation of anomalies at the base of the brain inherited congenitally, the characteristic of which are (1) extension of a tongue of cerebellar tissue posterior to the medulla and cord that extends into the cervical spinal canal; (2) caudal displacement of the medulla and the inferior part of the fourth ventricle into the cervical canal; and (3) a frequent but not invariable association with syringomyelia or a spinal developmental abnormality. Chiari recognized four types of abnormalities. Presently, the term has come to be restricted to Chiari's types I and II, that is, to cerebellomedullary descent without and with a meningomyelocele, respectively. The association of Arnold-Chairi malformation and high cervical cord infarction is unusual. The most common syndrome, anterior spinal artery syndrome (ASAS), is caused by interruption of blood flow to the anterior spinal artery, producing ischaemia in the anterior two-thirds of the cord, with resulting neurologic deficits. Causes of ASAS include aortic disease, postsurgical, sepsis, hypotension and thromboembolic disorders. The authors present an interesting case of cervical cord infarction due to anterior spinal artery thrombosis in a patient of type 1 Arnold-Chiari malformation without any of the above predisposing factors.