Cerebellar herniation in syringomyelia: relation between tonsillar herniation and the dimensions of the syrinx and the remaining spinal cord. A quantitative MRI study

Hundred Pediatric Cases Treated for Chiari Type II Malformation with Hydrocephalus and Myelomeningocele

Background Chiari malformation type II (CM-II) may not always present as an asymptomatic disorder but prove to be difficult in managing. This is especially true for neonates who show the worst prognosis. There is confounding data over whether shunting or craniocervical junction (CVJ) decompression should be employed. This retrospective analysis summarizes the results of 100 patients diagnosed and treated for CM-II along with hydrocephalus and myelomeningocele. Methods  We reviewed all the children who were diagnosed and surgically treated for CM-II at the Moscow Regional Hospital. Surgical timing was decided on the clinical conditions of each patient. Urgent surgery in the more compromised patients (usually infants) and elective surgery for patients with less severe conditions was performed. All patients first underwent CVJ decompression. Results  The retrospective review yielded 100 patients operated on for CM-II with concomitant hydrocephalus and myelomeningocele. The average herniation was 11.2 ± 5.1 mm. However, herniation level did not correlate with clinical findings. Concomitant syringomyelia was observed in 60% of patients. More severe spinal deformity was observed in patients with widespread syringomyelia ( p  = 0.04). In children of the younger age group, cerebellar symptoms and bulbar disorders were more frequently observed ( p  = 0.03), and cephalic syndrome was noted much less frequently ( p  = 0.005). The severity of scoliotic deformity correlated with the prevalence of syringomyelia ( p  = 0.03). Satisfactory results were significantly more often observed in patients of the older age group ( p  = 0.02). Patients with unsatisfactory results at the time of treatment were significantly younger ( p  = 0.02). Conclusion  If CM-II is asymptomatic, then no specific treatment is prescribed. If the patient develops pain in the occiput and neck, then pain relievers are prescribed. If a patient has neurological disorders or concomitant syringomyelia, hydrocephalus or myelomeningocele, surgical intervention is indicated. The operation is also performed if the pain syndrome cannot be overcome within the framework of conservative therapy.

[Features of syringomyelia natural course]

Rarity of syringomyelia (SM), a small amount of information about this disease leads to the lack of a unified concept of treatment and continuity between neurologists and neurosurgeons. Currently, there is no objective information on the timing, goals and objectives of surgery for SM, as well as the risks associated with this treatment.

AIM

Of this article was to study the natural course of syringomyelia and to determine in which part of the patients the disease progresses with time, how do the cysts' size change, and does this affect the condition of the patients, what symptoms appear first when the disease progresses? We retrospectively analyzed the medical records of 40 patients with SM who did not undergo surgery for various reasons (lack of indications, patient refusal from surgery, surgery was not offered to the patient, etc.) Clinical manifestations of the disease at the time of diagnosis were registered in 28 (70%) patients. Despite the conservative treatment, in 17 (60.7%) of them, symptoms began to progress over time. In 8 (28.6%) patients, the symptoms did not change during the observation; in 5 patients in this group, the disease clinically manifested in childhood, and did not progress in time after that. Three patients (10.7%) noted an improvement in their general condition, in two of them the syringomyelic cysts did not change according to MRI, and in one patient it regressed 2.5 years after it was found. Of the 12 patients without symptoms of the disease, within 62±13 months, only one patient (8.3%) developed sensory disorders in the hands, which eventually began to progress. Based on the data obtained, indications for surgery for SM are determined.

Chiari 1 deformity in children: etiopathogenesis and radiologic diagnosis

The metamerically associated normal hindbrain and normal posterior fossa are programmed to grow together in such a way that the tonsils are located above the foramen magnum and surrounded by the cerebrospinal fluid (CSF) of the cisterna magna. This allows the pulsating CSF to move freely up and down across the craniovertebral junction (CVJ). A developmental mismatch between the rates of growth of the neural tissue and of the bony posterior fossa may result in the cerebellar tonsils being dislocated across the foramen magnum. The cause of this may be, rarely, an overgrowth of the cerebellum. More commonly, it is due to an insufficient development of the posterior fossa, possibly associated with a malformation of the craniocervical joint. When it is not due to a remediable cause, such a herniation is called a Chiari 1 deformity. This definition is anatomic (descent of the tonsils below the plane of the foramen magnum) and not clinical: many patients with the deformity are and will remain asymptomatic. Most authors consider that a descent of 5 mm or more is clinically significant but other factors, such as the diameter of the foramen magnum and the degree of tapering of the upper cervical "funnel," are likely to be as important. Morphologic markers of severity on magnetic resonance imaging are, beside the degree of descent, the peg-like deformity of the tonsils, the obstruction of the surrounding CSF spaces (at the craniocervical junction and in the whole posterior fossa), a compression of the cord, an abnormal signal of the cord, and a syringomyelia, typically cervicothoracic. The syringomyelia is assumed to be explained by the "Venturi effect" that is associated with the increased velocity of the CSF across the restricted CSF spaces. Radiologically, the etiopathogenic assessment should address the size and morphology of the posterior fossa, and the functional status of the craniocervical flexion joint. The posterior fossa is best evaluated on sagittal cuts by the posterior fossa pentagon proportionality associated with the line of Chamberlain, and on coronal cuts, by showing a possible shallowness of the posterior fossa. The functional status of the craniocervical joint is altered in case of a proatlantal hypoplasia, as this condition results in a cranial shift of the joint that brings the tip of the dens and of the flexion axis in front of the medulla, that is, in a situation of osteoneural conflict. Less commonly, similar conflicts may also occur when an abnormal craniocervical segmentation results in an instability of the joint.

[Treatment of syringomyelia associated with Chiari 1 malformation]

Syringomyelia (SM) develops due to the disturbance of cerebrospinal fluid dynamics, spinal fixation or a spinal tumor. The disturbance of cerebrospinal fluid dynamics in the area of the foramen magnum leads to the progression of SM in Chiari 1 malformation (CM1). CM1 is the most prevalent pathology of craniovertebral junction associated with SM. The prevalence of CM1 varies from 3 to 8 per 100 000 population but SM is diagnosed in 65% of patients with CM1. Clinical symptoms of CM1 and SM include pain in the occipital area, gait disturbances due to sensitive ataxia, dissociated sensory disorders, dysphagia, paresis of the extremities. In most patients, symptoms of SM progressed over the years. The diagnosis is based on MRI results of the brain and spinal cord. Phase-contrast MRI is used to study the disturbance of cerebrospinal fluid dynamics in details. Progression of SM or CM1 symptoms needs surgical treatment - decompression of the posterior cranial fossa for the recovery of normal cerebrospinal fluid dynamics.

Clinical, radiological, and genetic similarities between patients with Chiari Type I and Type 0 malformations

OBJECT

Although Chiari Type I (CM-I) and Type 0 (CM-0) malformations have been previously characterized clinically and radiologically, there have been no studies focusing on the possible genetic link between these disorders. The goal of this study was to identify families in whom CM-0 and CM-I co-occurred and to further assess the similarities between these disorders.

METHODS

Families were ascertained through a proband with CM-I. Detailed family histories were obtained to identify first-degree relatives diagnosed with CM-0. Several criteria were used to exclude individuals with acquired forms of CM-I and/or syringomyelia. Individuals were excluded with syndromic, traumatic, infectious, or tumor-related syringomyelia, as well as CM-I due to a supratentorial mass, hydrocephalus, history of cervical or cranial surgery unrelated to CM-I, or development of symptoms following placement of a lumbar shunt. Medical records and MR images were used to characterize CM-I and CM-0 individuals clinically and radiologically.

RESULTS

Five families were identified in which the CM-I proband had a first-degree relative with CM-0. Further assessment of affected individuals showed similar clinical and radiological features between CM-0 and CM-I individuals, although CM-I patients in general had more severe symptoms and skull base abnormalities than their CM-0 relatives. Overall, both groups showed improvement in symptoms and/or syrinx size following craniocervical decompression surgery.

CONCLUSIONS

There is accumulating evidence suggesting that CM-0 and CM-I may be caused by a common underlying developmental mechanism. The data in this study are consistent with this hypothesis, showing similar clinical and radiological features between CM-0 and CM-I individuals, as well as the occurrence of both disorders within families. Familial clustering of CM-0 and CM-I suggests that these disorders may share an underlying genetic basis, although additional epigenetic and/or environmental factors are likely to play an important role in the development of CM-0 versus CM-I.

Pathogenesis of syringomyelia associated with Chiari type 1 malformation: review of evidences and proposal of a new hypothesis

The exact pathogenesis of syringomyelia associated with Chiari type 1 malformation is unknown, although a number of authors have reported their theories of syrinx formation. The purpose of this review is to understand evidences based on the known theories and to create a new hypothesis of the pathogenesis. We critically review the literatures on clinicopathological, radiological, and clinical features of this disorder. The previously proposed theories mainly focused on the driven mechanisms of the cerebrospinal fluid (CSF) into the spinal cord. They did not fully explain radiological features or effects of surgical treatment such as shunting procedures. Common findings of the syrinx in clinicopathological studies were the communication with the central canal and extracanalicular extension to the posterior gray matter. Most of the magnetic resonance imaging studies demonstrated blockade and alternated CSF dynamics at the foramen magnum, but failed to show direct communication of the syrinx with the CSF spaces. Pressure studies revealed almost identical intrasyrinx pressure to the subarachnoid space and decreased compliance of the spinal CSF space. Recent imaging studies suggest that the extracellular fluid accumulation may play an important role. The review of evidences promotes a new hypothesis of syrinx formation. Decreased absorption mechanisms of the extracellular fluid may underlie the pathogenesis of syringomyelia. Reduced compliance of the posterior spinal veins associated with the decreased compliance of the spinal subarachnoid space will result in disturbed absorption of the extracellular fluid through the intramedullary venous channels and formation of syringomyelia.

The post-syrinx syndrome: stable central myelopathy and collapsed or absent syrinx

Among 168 cases with neurologic findings of cervicothoracic syringomyelia and MRI findings of Chiari 1 malformation and/or underdevelopment of the posterior cranial fossa, 15 patients (9.1 %) had collapsed, flat syrinxes and 14 patients (8.3 %) did not have syrinxes. Both groups of patients had clinical findings of central myelopathy that had been stable for at least 3 years. Magnetic resonance imaging detected atrophy of the cervical spinal cord in both groups and spontaneous communications between the syrinx and the subarachnoid space in 3 patients of the group with collapsed syrinxes. Analysis of these results and review of the literature suggest that patients with clinical signs of syringomyelia and Chiari 1 malformation or underdeveloped posterior fossa, but with small or absent syringomyelitic cavities, have the "postsyrinx" state as a result of spontaneous collapse of distended syrinxes.

Clinical and neuroimaging features of "idiopathic" syringomyelia

In some adult patients with cervical syringomyelia, MRI studies do not identify primary disease within the foramen magnum or spinal canal. To identify the etiology of this idiopathic type of syringomyelia, clinical features and posterior fossa (PF) measurements from 17 of these patients, 17 patients with Chiari I-type syringomyelia, and 32 control subjects were compared. Idiopathic syringomyelia and Chiari I-type syringomyelia manifested central cervical myelopathy and a small PF with narrow CSF spaces, suggesting that they develop by the same mechanism.

Syrinx size and duration of symptoms predict the pace of progressive myelopathy: retrospective analysis of 103 unoperated cases with craniocervical junction malformations and syringomyelia

OBJECTIVE

the clinical course of syringomyelia associated with craniocervical junction abnormalities is variable. About half of the unoperated patients have benign course. This is difficult to explain on the basis of the present pathogenetic theories. Therefore, to understand the mechanism of syrinx progression better, we studied the value of syrinx size, syrinx morphology, and the syrinx/spinal cord size ratio in predicting the rate of progression and the severity of myelopathy in these patients.

METHODS

103 adult patients with syringomyelia associated with Chiari 1 malformation and/or radiographic signs of underdeveloped posterior cranial fossa were clinically and MRI examined. Patients were subdivided according to the type of disease progression. Severity of neurological deficits, and MRI features (the extent of cerebellar tonsillar displacement, anteroposterior diameter of cavities, the spinal cord and cyst/cord ratio and the shape of cavities) were measured.

RESULTS

a significant relationship was found between the mid-sagittal diameter of the syrinxes and the type of disease course; patients with short duration and rapid progression had the largest diameters of cavities, whereas patients with longer duration as well as with slow rate of progression had smaller diameters (chi(2)=28.90, P<0.05; chi(2)=29.89, P<0.01; r=-0.24, P<0.05). In addition, a correlation was found between the anteroposterior diameter of the spinal cord and cyst/cord ratio and the disease duration (r=0.52, P<0.05 and r=0.48, P<0.05, respectively).

CONCLUSIONS

the initial years for the development of symptomatic syringomyelia associated with CCJ malformations are characterized by relatively rapid clinical progression accompanied with distended cavities. In the later periods of unoperated syringomyelia, some patients show delay in the progress of syrinxes accompanied with collapse of cavities, probably either due to a spontaneous formation of drainage between the syrinx and the subarachnoidal space, or due to the restoration of abnormal CSF dynamics at the CCJ level.

Asymptomatic Chiari Type I malformations identified on magnetic resonance imaging

OBJECT

Chiari Type I malformation (CMI) is a congenital disorder recognized by caudal displacement of the cerebellar tonsils through the foramen magnum and into the cervical canal. Frequently, associated findings include abnormalities of nearby bony and neural elements as well as syringomyelia. Cerebellar tonsillar ectopia is generally considered pathological when greater than 5 mm below the foramen magnum. However, asymptomatic tonsillar ectopia is an increasingly recognized phenomenon, the significance of which is poorly understood.

METHODS

The authors retrospectively reviewed the records of all brain magnetic resonance (MR) images obtained at our hospital over a 43-month period in an attempt to ascertain the relative prevalence and MR imaging characteristics of asymptomatic CMIs. Of 22,591 patients who underwent MR imaging of the head and cervical spine, 175 were found to have CMIs with tonsillar herniation extending more than 5 mm below the foramen magnum. Of these, 25 (14%) were found to be clinically asymptomatic. The average extent of ectopia in this population was 11.4 +/- 4.86 mm, and was significantly associated with a smaller cisterna magna. Syringomyelia and osseous anomalies were found in only one asymptomatic patient.

CONCLUSIONS

The authors suggest that the isolated finding of tonsillar herniation is of limited prognostic utility and must be considered in the context of all available clinical and radiographic data. Strategies for treating patients with asymptomatic CMIs are discussed.