Current surgical treatment of Chiari type I malformation and Chiari I-syringomyelia complex

Chiari type I malformation and so-called Chiari-I/syringomyelia complex continue to inspire controversy. Disagreement on these malformations concern both etiopathogenesis and treatment. Our still poor understanding of the natural course of the disease, the lack of consensus regarding therapeutic indications and even disagreement on appropriate surgery all contribute to cause disagreement. Significant progress has been made in our understanding of contributing etiopathogenetic factors in recent years. The most widely accepted hypothesis is that anomalous embryonic development characterized by paraxial mesodermal insufficiency would put volumetric constraints on postnatal development of the posterior fossa. We review historical and current controversies regarding Chiari type I malformation and classic theories on causative and contributing factors. We also discuss the latest surgical treatments that have been suggested, as well as associated anomalies--mainly syringomyelia, hydrocephalus and malformed cranial-cervical articulation. Finally, we propose a protocol useful for the diagnosis and treatment of Chiari type I malformation associated with dilation of the ventricular system.     

Otoneurological manifestations in Chiari-I malformation

The type I Chiari malformation consists of a caudal displacement of the cerebellar tonsils through the foramen magnum into the cervical spinal canal. The most common presenting symptoms, such as pain, weakness and headache, are frequently preceded by otoneurological symptoms. Sensorineural hearing loss, vertigo, nystagmus, dysequilibrium, tinnitus and other cranial nerve involvement have been reported in Chiari-I malformation. A case report is presented and the clinical features of the disease are discussed with emphasis on the otoneurological aspects.     

Audio-vestibular manifestations of Chiari malformation and outcome of surgical decompression: a case report

Sensorineural hearing loss, tinnitus, dizziness and ataxia are recognised symptoms associated with Chiari malformations but they are rarely the presenting complaints. Patients with such symptoms are frequently referred to otolaryngologists and audiological physicians. We report a case of a 13-year-old girl who presented complaining of tinnitus and impaired hearing, and was subsequently diagnosed as having a type I Chiari malformation. Pure tone audiogram showed a mild hearing impairment on the left side and the speech audiogram was normal. Auditory brain stem responses and the electronystagmography were abnormal. The patient underwent posterior fossa decompression following which her tinnitus disappeared, the hearing problem recovered and some of the abnormal electrophysiological parameters were corrected.     

One-step fluorescent probe product-enhanced reverse transcriptase assay

The Chiari type II malformation is the leading cause of death in infants with myelomeningocele. The authors report 17 cases of symptomatic Chiari type II malformation occurring in two distinct age dependent population. In Group I, 13 neonates and infants in the first year of life presented with cranial nerve and brain stem dysfunction characterized by vocal cord paralysis, apnea, dysphagia and laryngeal stridor. In Group II, 4 patients developed signs and symptoms after the first year of life. In this group, the presentation was more insidious and included neck pain and cerebellar manifestations. The surgical treatment consisted initially in shunt implantation or revision and when there was no improvement, posterior fossa decompression was performed. The response to the surgical treatment differed considerably between the two groups: older patients improved promptly after surgery and there was no casualties; in newborn and infants, especially those under 6 months of age, the mortality rate was 46.1%. The authors stress that prompt diagnosis and surgical intervention should be performed in order to produce a favorable outcome.     

Chiari Type I malformation and syringomyelia in unrelated patients with blepharophimosis. Report of two cases

Syringomyelia is a rare, mainly sporadic disease of the spinal cord, which is associated with 80% of cases in which a Chiari Type I malformation is also present. A mendelian transmission of syringomyelia (autosomal dominant or recessive) has been proposed in approximately 2% of reported cases. The association of syringomyelia with hereditary diseases (Noonan's syndrome, phacomatoses) has been mentioned frequently in the literature. The authors report the presence of a Chiari Type I malformation accompanied by syringomyelia in two unrelated patients affected by a familial Type II blepharophimosis-ptosis-epicanthus inversus syndrome (BPES). The first patient was a 35-year-old woman who presented with a right C-8 root paresia. The second case involved a 20-year-old man who complained of cervical radicular pain. Both belong to families in which BPES was segregated in an autosomal dominant modality, but other family members had no known neurological symptoms. To the authors' knowledge, such a combination has never been described. Perhaps the possible involvement of a genetic component in some cases of Chiari Type I-associated syringomyelia will someday be debated.     

Chiari malformations and hydrosyringomyelia

INTRODUCTION: The association of hindbrain herniation, better known as Chiari malformation, and cystic cavitation of the spinal cord or hydrosyringomyelia has been well described in the literature although there is little consensus regarding its etiology, pathophysiology or optimal treatment. DEVELOPMENT: Despite a well-accepted and utilized classification system of both Chiari malformation and hydrosyringomyelia, there remains considerable disagreement regarding the proper management of these patients. CONCLUSIONS: This article reviews several popular theories on the etiology and pathophysiology of this disorder, briefly discusses the clinical features and radiologic findings associated with Chiari malformation and hydrosyringomyelia, and reviews basic surgical techniques for decompression of the cranial-cervical junction and treatment of the hydrosyringomyelia.     

Hydrodynamics of syringomyelia

Abnormality of CSF hydrodynamics is an important factor of the pathogenesis of syringomyelia. Recent development of cine-MRI visualized real time CSF movement in the syrinx or subarachnoid space. In the present study, twenty cases of syringomyelia associated with Chiari I malformation, 10 cases of syringomyelia associated with spina bifida aperta, and 10 cases of syringomyelia associated with spina bifida occulta were studied with MRI and cine-MRI. The result demonstrated that hydrodynamics of these three groups were different to each other. Chiari I malformation showed CSF hydrodynamic abnormality at the foramen magnum and marked flow void in the syrinx. On the other hand, myelomeningocele showed hydrocephalus and less prominent flow void in the syrinx. Spinal lipoma which is the majority of spina bifida occulta showed no abnormality of CSF hydrodynamics. In conclusion, the selection of treatments should be individualized depending on the hydrodynamical abnormality of each patient.     

Chiari I malformation associated with syringomyelia and scoliosis

STUDY DESIGN: A retrospective review of a series of 12 children who underwent suboccipital foraminotomy and duroplasty for Chiari I malformation. OBJECTIVE: To assess the effects of this surgery on associated syringomyelia and scoliosis. SUMMARY OF BACKGROUND DATA: Suboccipital foraminotomy for the treatment of syringomyelia associated with Chiari I malformation was greatly stimulated by Gardner's hydrodynamic theory, and its results proved to be encouraging. However, several authors reported improvement or stabilization of associated scoliosis after this surgery. METHODS: A retrospective review was conducted on 12 patients who underwent suboccipital foraminotomy for Chiari I malformation associated with syringomyelia. Neurologic Impairment, extent of syringomyelia, and severity of associated spinal deformity were assessed preoperatively and at a 4.5-year average follow-up (range, 2.1-12 years). Anomaly of superficial abdominal reflexes was found in all cases, and para or tetraparesis in three cases. Syringomyelia was of variable localization and extent. Scoliosis was present in 7 cases (greater than 40 degrees in 5 cases). RESULTS: Diminution or complete disappearance of syringomyelia was observed in 11 cases, 3 months to 1 year after surgery. Superficial abdominal reflexes anomaly improved in four cases. Minimal neurologic deficit persisted in one case. Scoliosis improved in one case, remained unchanged in one case, and progressed in the five cases with preoperative severe deformity, requiring instrumentation and fusion. CONCLUSIONS: Improvement of syringomyelia and neurologic deficit, observed with suboccipital foraminotomy, supports the theory that abnormal hydrodynamics of the cerebral spinal fluid is most likely to cause these deficits.     

Surgical technique for cranio-cervical decompression in syringomyelia associated with Chiari type I malformation

Our purpose is to present our results with the surgical treatment of syringomyelia associated with Chiari type I malformation. Between October 1989 and October 1995, twenty-eight patients underwent a sub-occipital craniotomy and a C1 laminectomy. After dura mater opening the cerebellar tonsils were mobilised. Neither catheter, nor plugging of the obex, nor tonsillar tissue removal was performed. The dura mater was enlarged by means of a wide graft to create a new cisterna magna of adequate size. Postoperative MRI scans showed an ascent of the cerebellum of 4.3 +/- 4.8 mm (measured by the fastigium to basal line), as well as of the brainstem (mean migration of the mesencephalon-pons junction of 4.3 +/- 3.3 mm). The tonsils emigrated cranially 6.5 +/- 4.8 mm. While preoperative mean syringo-cord ratio was 66.3% +/- 13.3, post-operatively was 12.1% +/- 12.7 (p < 0.0001). A complete collapse of the syrinx was observed in 39% of the patients. Long-term improvements were obtained in 73% of the cases and 27% were unchanged. No patient got worse. We conclude that in the treatment of syringomyelia associated with Chiari I malformation an artificial cisterna magna of sufficient size must be created. This is achieved by means of an extensive sub-occipital craniotomy and C1 laminectomy, followed by dural opening. Small bone removal with limited enlargement of the posterior fossa often results in failures of treatment and recurrences. Tonsillar removal is not necessary to obtain a good reconstruction of the cisterna magna.     

Technique of lateral canthoplasty for the correction of macropalpebral fissure in the dog

Chiari III malformations are extremely rare hindbrain malformations that are associated with a high early mortality rate, or severe neurologic deficits in the survivors. The preferred treatment is early operative closure and CSF shunting. We report a case of a newborn infant with a Chiari III malformation with displacement of the brainstem and cerebellum into the cervical encephalocele which precluded immediate operative closure of the defect. Instead, a ventriculoperitoneal shunt was placed and the patient was followed with serial imaging studies. The child survived. The shunt allowed the brainstem and cerebellum to regress into the cervical spinal canal as the dilated cerebral aqueduct and fourth ventricle decompressed. A delayed closure of the cervical encephalocele was performed at 30 months of age. Cerebrospinal fluid diversion with delayed closure may be an option for large lesions.     

Clinical and neuroimaging features of Chiari type I malformations with and without associated syringomyelia

The clinical and neuroimaging characteristics of 22 consecutive patients with Chiari type I malformations were evaluated to investigate the pathogenesis of syrinx formation. All patients underwent magnetic resonance imaging and x-ray tomography before surgery. The electric manometric Queckenstedt test was performed on 16 patients pre- and postoperatively. Syringomyelia was present in 17 patients and absent in five patients. All patients without syringomyelia suffered from foramen magnum compression syndrome, with a wider basal angle, more acute clivo-axial angle, shorter clivus, and more prominent tonsillar ectopia than patients with syringomyelia. Low brain stem position, basilar impression, and beaking of the cervicomedullary junction were also more prominent in patients without syringomyelia. Marked to complete block with the neck in flexed position by Queckenstedt test was present in all patients except one. Patients with Chiari malformation not associated with syringomyelia have more pronounced compression of the brain stem at the foramen magnum. Therefore, despite a block of the cerebrospinal fluid pathway at the foramen magnum, syrinx formation may be prevented by severe compression.     

Simplified hepatic resection utilizing absorbable polyglycolic acid-based tape and other ligature apparatus

Central nervous system malformations have been reported in a number of inherited enzyme defects. Ethylmalonic encephalopathy, an organic aciduria of unknown pathogenesis, has not been reported previously in association with brain or spinal cord malformations. We report on 2 sibs with confirmed ethylmalonic encephalopathy and malformations of the central nervous system; one with tethered cord, the other with cerebellar tonsillar ectopia (Chiari I malformation).     

Isolated partial growth hormone deficient short stature with syringomyelia not associated with birth injury

A 59-year-old female with 20-year history of slowly progressing muscle atrophy and sensory disturbance of upper extremities showed short stature, scoliosis, hunger type of sensory dissociation of the upper extremities and pyramidal tract sign of the lower extremities. Magnetic resonance imaging (MRI) clarified hypoplasia of the anterior pituitary lobe, Arnold-Chiari malformation and cervical syringomyelia. Insulin and arginine stimulating tests revealed partial type of isolated growth hormone (GH) deficiency but GH gene analysis detected no defects of GH genes. It was considered to be a rare case of non-hereditary hypopituitarism with Chiari malformation and syringomyelia not associated with perinatal injury, namely a midline anomaly syndrome.     

Primary craniovertebral anomalies and the hindbrain herniation syndrome (Chiari I): data base analysis

This prospective study analyzes 100 patients with Chiari malformation and primary craniovertebral junction (CVJ) anomalies (3-66 years). Neurodiagnostic investigations employed tomography, gas myelography, CT and CT myelography, and MRI. Factors considered were reducibility, mode of encroachment, cerebrospinal fluid (CSF) dynamics and syringohydromyelia. Sixty-six patients with irreducible pathology underwent ventral or ventrolateral decompression and dorsal stabilization. Dorsal occipitocervical fixation was performed in reducible lesions that also required dorsal decompression (n = 34). Proatlas remnants were identified in 8 and atlas assimilation in 92 patients. Paramesial invagination was present in 20, syringohydromyelia in 46, and vertebral segmentation defects in 66 others. Completely reducible abnormalities were identified in 16 of 20 patients aged 2-14 years, and partially reducible abnormalities in 4 of 16 patients aged 14-20 years, 8 of 48 patients aged 20-40 years and 6 of 16 patients aged 40-60 years. The critical sagittal canal diameter at the foramen magnum was 19 mm. Twenty-two patients had previous posterior decompression and 27 had previous syrinx to subarachnoid shunt with delayed deterioration. Improvement occurred in all after ventral or ventrolateral decompression with resolution of the syringohydromyelia and normalization of CSF flow. We conclude that: (1) hindbrain herniation syndrome is frequently seen with fourth occipital sclerotome abnormalities; (2) Chiari malformation with craniovertebral abnormalities become symptomatic with a canal diameter of < 19 mm; (3) abnormal ventral bony pathology is reducible in children wit atlas assimilation and later becomes irreducible invagination, therefore early operation with fusion is recommended; (4) ventral decompression relieves brain stem, cerebellar symptoms and syringohydromyelia; (5) CSF studies with cine MRI shows reversal of craniospinal CSF dissociation after ventral CVJ decompression and; (6) craniovertebral anomalies associated with Chiari malformations must be addressed early and appropriately.     

The outcome of adjusted accumulation dose of treatment of Graves'' disease

Etiology of syringomyelia associated with Chiari type I malformation has been unknown. Moreover, the surgical procedure of foramen magnum decompression for this type of syringomyelia has not been standardized yet. No one procedure has been always successful, leading to many alternative procedures. The purpose of the present study is to elucidate pathway of cerebrospinal fluid into the syrinx cavity and to find out the best procedure for this disease. Fourty two patients with syringomyelia associated with Chiari type I malformation, which were diagnosed with magnetic resonance imaging (MRI), underwent surgical treatment. In all patients, craniocervical junction anomalies, cervical disc herniation and other spinal diseases were ruled out. There were 26 men and 16 women, ranging from 6 to 72 (mean: 42.3) years in age. The size, length and position of upper end of each syrinx cavity and the degree of the tonsillar herniation were measured on preoperative T1-weighted image and were compared each other. There were no significant relationship between the degree of tonsillar herniation and the size, length and position of syrinx cavity. No case showed that the upper end of syrinx cavity communicated to the 4th ventricle. The results suggest that the pathway of cerebrospinal fluid into the the syrinx cavity was not central canal from the 4th ventricle but microcanals in the spinal cord. All patients were carried out with foramen magnum decompression, which was divided into 4 groups according to the degree of decompression: 1) tonsillectomy group: 12 patients underwent subocciptital craniectomy (SOC) with patcy-graft dural plasty using lyophilized dura mater and tonsillectomy, 2) lysis group: 7 underwent SOC, dural plasty and microsurgical lysis of arachnoidal trabecula and fibrinoid filament around herniated tonsil, 3) plasty group: 17 underwent SOC and dural plasty and 4) dural group: 6 underwent SOC and removal of the outer layer of the dura mater. The mean follow-up periods were 3.7 years in tonsillectomy group, 3.6 years in lysis group, 2.3 years in plasty group, 1.8 years in dural group, respectively. Evaluation of the result following four types of surgical treatments was performed on clinical symptoms and the volume of syrinx cavity on sagittal MRI. The ratio in the area of the syrinx and spinal cord on preoperative and postoperative sagittal MRI were measured. There was no significant difference among 4 groups on the degree of reduction of syrinx in the sagittal plane as evaluated on MRI, whereas with regards to improvement of the clinical symptoms, dural group was significantly worse than the other three groups. The surgical procedure of dural plasty was clearly less invasive than those of tonsillectomy and lysis of subarachnoidal trabecula. These results suggest that we should select dural plasty as a primary surgical procedure for syringomyelia associated with Chiari type I malformation.     

Posterior fossa decompression without duraplasty in infants and young children for treatment of Chiari malformation and achondroplasia

Some children with Chiari malformation and achondroplasia require posterior fossa decompression that typically includes expansion of the dural tube with duraplasty. Infants and young children, however, may have a more distensible dura mater than do older patients. Furthermore, the structures that compress the hindbrain of young patients may be the bone and abnormally thickened atlantooccipital membrane, i.e., dural band, rather than the dura mater. We have treated 7 children who had Chiari malformation or achondroplasia with posterior fossa decompression without duraplasty. All children were symptomatic; 3 had Chiari-I malformations, 2 Chiari-II malformations, and 2 achondroplasia. The age range was 3 months to 2.5 years (mean 15.1 months). The exent of tonsillar herniation and other hindbrain anomalies was assessed on preoperative magnetic resonance imaging. The infants with Chiari-II malformations underwent cervical laminectomies, whereas the other young children with Chiari-I malformations or achondroplasia underwent suboccipital craniectomy as well as cervical laminectomy. In Chiari malformation, the dural band was divided; in achondroplasia, there was no identifiable dural band. Following bony decompression and division of the identifiable dural band, immediate expansion of the stenotic region with visible cerebrospinal fluid space posterior to the neural elements could be ascertained by intraoperative ultrasonography. During a follow-up period ranging from 4.5 months to 4 years (mean 22 months), all patients made improvements in their symptoms, 3 having complete resolution of their symptoms. This preliminary experience indicates that in children 2 years of age or younger, posterior fossa bony decompression without duraplasty can be effective treatment for Chiari malformations or achondroplasia.     

Surgical complications of open spinal dysraphism

The embryogenesis, closure technique, and preoperative preparation of open myelomeningocele are described in this article. Both early and late complications of myelomeningocele closure are discussed with respect to predisposing factors, diagnosis, treatment, and prevention. These complications include worsened neurological level, wound dehiscence, wound infection, cerebrospinal fluid leak, postoperative ileus, symptomatic Chiari malformation, shunt infection, necrotizing enterocolitis, and problems related to kyphectomy.     

Frontal foramina in pediatric skull in cases of congenital hydrocephalus

PURPOSE: To describe a new observation, frontal calvarial foramina, in pediatric patients with congenital hydrocephalus secondary to central nervous system malformation. MATERIALS AND METHODS: Frontal foramina were initially identified in three female patients with Chiari II malformation. Subsequently, head computed tomographic (CT) scans in 99 patients with congenital hydrocephalus were retrospectively reviewed. CT scans in a control group of 116 patients without hydrocephalus were also retrospectively reviewed. RESULTS: Frontal foramina were found in eight of 61 (13%) patients with Chiari II malformation, in one child with Dandy-Walker malformation, and in one child with occipital horn dilatation (colpocephaly), but not in control patients. Sequential CT examinations in three patients with frontal foramina depicted gradual closure after ventriculoperitoneal shunt placement. CONCLUSION: Frontal foramina may represent an abnormality variably expressed in certain central nervous system malformations that cause congenital hydrocephalus. The presence of frontal foramina palpated or visualized on plain radiographs may help in the diagnosis of congenital hydrocephalus and central nervous system malformation.     

Presentation and management of Chiari I malformation in children

To determine the efficacy of operative treatment for children with Chiari I malformation, the medical records and magnetic resonance imaging (MRI) studies of 68 consecutive patients cared for at The Children's Hospital, Boston, Mass., USA, from December, 1988 to November, 1996 were retrospectively reviewed. All patients underwent suboccipital craniectomy, C1 laminectomy, and dural grafting. Bipolar coagulation to shrink and reduce the volume of the cerebellar tonsils was carried out in 40 patients. In 32 of 40 patients with associated syringomyelia, the procedure included placement of a IVth ventricle to cervical subarachnoid space shunt. Twenty-three patients with syringomyelia also had plugging of the obex. There was no operative mortality. Morbidity included a 22% incidence of nausea/vomiting and a 10% incidence of headache, both limited to the immediate postoperative period. Within the first postoperative month, all patients or their parents reported clear improvement in their presenting symptoms and 93% were found to have clear improvement in their presenting signs. In follow-up periods of 6-70 months, all patients had continued unequivocal symptom improvement and all patients were found on examination to have clear improvement in neurological signs. In patients with syringomyelia, MRI studies carried out at least 6 months postoperatively revealed near total or total syrinx resolution in 80% of the cases. This study demonstrates that a standard bony and dural decompression of the foramen magnum region with modifications designed to maximize the restoration of CSF circulation across the foramen magnum is a safe, effective operative treatment for Chiari I malformation in children.     

Spondylolysis associated with Arnold-Chiari malformation and syringomyelia. A report of two cases

STUDY DESIGN: This is a report of two cases. OBJECTIVE: To document the occurrence and association of spondylolysis and Arnold-Chiari malformation Type I. SUMMARY OF BACKGROUND DATA: The association of spinal dysraphism has been reported with Arnold-Chiari Type II, but not with Arnold-Chiari Type I. METHODS: The senior author was involved in the care of these patients. All medical records, laboratory and radiologic investigations, and related literature were reviewed. RESULTS: The presence of cephalic and caudal neuropore maldevelopment may be present in various combinations. The presence of spondylolysis, with or without spina bifida occulta, associated with Arnold-Chiari malformation type I and syringohydromyelia, is demonstrated. CONCLUSIONS: In some patients, the presence of spondylolysis may represent a congenital anomaly and may be associated with cephalic neuropore maldevelopment, such as cerebromedullary malformation syndrome (i.e., Arnold-Chiari malformation Type I).