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Open access

Secondary Chiari malformation due to enlarged spinal arachnoid villi–like structure: illustrative case

Izumi Koyanagi, Yasuhiro Chiba, Hiroyuki Imamura, Masami Yoshino, and Toshimitsu Aida

BACKGROUND

Secondary Chiari malformation can be caused by various disorders associated with cerebrospinal fluid (CSF) leakage at the spinal level. In this report, the authors describe a rare case of secondary Chiari malformation caused by excessive CSF absorption through the enlarged spinal arachnoid villi–like structure.

OBSERVATIONS

A 20-year-old woman presented with progressive severe headache and posterior neck pain. Magnetic resonance imaging showed tonsillar herniation and decreased subarachnoid space around the spinal cord. A hypointense signal area was observed in the ventral spinal canal on a T2-weighted image. An axial image revealed multiple small, arachnoid cyst–like structures at the right T1 nerve root sleeve. Direct surgery revealed that the cyst-like structures were continuous with the arachnoid membrane and protruded into the abnormally large epidural venous sinus. The cyst-like structures were resected, and the dural sleeve was repaired using fascia. The patient showed good improvement of symptoms after surgery.

LESSONS

Excessive CSF absorption through the enlarged spinal arachnoid villi–like structure can cause secondary Chiari malformation. Neurosurgeons should be aware of this unusual mechanism of CSF leakage. Simple posterior fossa decompression will be ineffective or even harmful.

Open access

Chiari malformation type 1: are we doing less with more? Illustrative case

Giuseppe Talamonti, Erika Ferrari, and Giuseppe D’Aliberti

BACKGROUND

Classic treatment of Chiari malformation type 1 consists of foramen magnum decompression. Selected patients may require occipitocervical fixation, transoral odontoidectomy, tonsillectomy, and so forth. Treatment standardization does not yet exist, and some patients risk being overtreated.

OBSERVATIONS

A 20-year-old man with headache and Chiari malformation type 1 underwent extradural bone decompression. One year later, he was managed with the extradural section of his filum terminale. Eighteen months later, the patient underwent monitoring of intracranial pressure, occipitocervical stabilization, transoral odontoidectomy, minimally invasive subpial tonsillectomy, and occipital cranioplasty. His headache never changed, and he progressively developed hemiparesis and swallowing and respiratory disturbances. Two years later, a new magnetic resonance imaging scan showed extended syringomyelia with scarce peritonsillar subarachnoid space. The umpteenth operation consisted of the removal of a constricting epidural scar, arachnoid dissection, total tonsillectomy, creation of a wide subarachnoid space, and dural sac augmentation. The patient’s initial postoperative course was smooth, and his headache improved. However, 8 days after surgery, the patient acutely presented with vegetative disturbances and died because of malignant brainstem edema of unknown origin.

LESSONS

The story of this patient is not so uncommon. He underwent all the possible surgical treatments rather than a timely adequate osteodural decompression. Probably, he received less with more.

Open access

Noninvasive evaluation of craniovertebral junction instability in 2 patients following Chiari decompression with rigid C-collar immobilization: illustrative cases

Kerrin S. Sunshine, Theresa A. Elder, and Krystal L. Tomei

BACKGROUND

The complex Chiari malformation has been identified in a subset of Chiari patients at higher risk for worsening symptoms following Chiari decompression. Although parameters such as the clivoaxial angle and the perpendicular distance of the dens to the line from the basion to the inferoposterior part of the C2 body (pBC2) have been evaluated to help with the prediction of risk, the decision to pursue an occipitocervical fusion in lower-risk patients does not come without inherent risk.

OBSERVATIONS

The authors present 2 patients who had symptoms of worsening ventral brainstem compression following Chiari decompression, neither of whom was categorized in the highest risk category for occipitocervical instability. In addition, neither patient had gross instability on radiographic imaging. A trial with rigid C-collar immobilization provided relief of symptoms in both patients and allowed reassurance of the likelihood of success of occipitocervical fusion.

LESSONS

In patients without clear radiographic instability following Chiari decompression, a C-collar trial may provide a noninvasive option for assessing the potential success of occipitocervical fusion.

Open access

Spontaneous syrinx resolution in patient with Chiari I malformation: illustrative case

Elizabeth Gallo, Gazanfar Rahmathulla, Dinesh Rao, Kourosh Tavanaiepour, and Daryoush Tavanaiepour

BACKGROUIND

Chiari malformations include a spectrum of congenital hindbrain herniation syndromes. In patients with the most common subtype, Chiari malformation Type I, 50% to 75% develop a syrinx. The pathogenesis of syringomyelia is not well understood, with multiple theories outlined in the literature. Although the presence of a syrinx in a patient with Chiari malformation is generally accepted as an indication for surgical intervention, there are documented cases of spontaneous resolution that support a more conservative approach to management.

OBSERVATIONS

The authors reported a case of spontaneous resolution of a cervical syrinx in an adult with an unchanged Chiari malformation.

LESSONS

Given the possibility of spontaneous resolution over time, the authors believe a more conservative approach of observation with periodic surveillance, magnetic resonance imaging, and neurological examination should be considered in the management of a patient with a Chiari malformation and associated syringomyelia.

Open access

Spontaneous intracranial hypotension secondary to congenital spinal dural ectasia and genetic mosaicism for tetrasomy 10p: illustrative case

Peyton L. Nisson, Rhona Schreck, John M. Graham Jr., Marcel M. Maya, and Wouter I. Schievink

BACKGROUND

Spontaneous intracranial hypotension has historically been a poorly understood pathology that is often unrecognized and undertreated. Even more rarely has it been described in pediatric patients with an otherwise benign past medical history.

OBSERVATIONS

Herein the authors describe one of the youngest patients ever reported, a 2-year-old girl who developed severe headaches, nausea, and vomiting and experienced headache relief after lying down. Imaging revealed tonsillar herniation 14 mm below the foramen magnum, presumed to be a Chiari malformation, along with extensive dural cysts starting from thoracic level T2 down to the sacrum. She was found to have streaky skin pigmentary variation starting from the trunk down to her feet. Genetic analysis of skin biopsies revealed mosaicism for an isodicentric marker chromosome (10p15.3–10q11.2 tetrasomy) in 27%–50% of cells. After undergoing a suboccipital and cervical decompression at an outside institution, she continued to be symptomatic. She was referred to the authors’ hospital, where she was diagnosed with spontaneous intracranial hypotension.

LESSONS

After receiving a series of epidural blood patches, the patient experienced almost complete relief of her symptoms. To the authors’ knowledge, this is the first time this chromosomal anomaly has ever been reported in a living child, and this may represent a new genetic association with dural ectasia.

Open access

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

Jorn Van Der Veken, Marguerite Harding, Saba Hatami, Marc Agzarian, and Nick Vrodos

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.

Open access

Delayed chemical meningitis after Chiari decompression with duraplasty: illustrative cases

Orgest Lajthia, Mithun G. Sattur, and Abhay K. Varma

BACKGROUND

Dural reconstruction to achieve expansion duraplasty is important in suboccipital decompression for Chiari malformation type 1 (CM1). Although various dural substitutes are available, including synthetic collagen matrix grafts and dural xenografts, they have the potential to induce an inflammatory response. In this case series, the authors present their experience and discuss the incidence and possible mechanism of aseptic meningitis after the use of bovine collagen matrix graft as a dural substitute in patients with CM1 after suboccipital decompression.

OBSERVATIONS

Three consecutive adult female patients who underwent suboccipital decompression at a single institution by a single neurosurgeon were retrospectively reviewed. They all presented with signs of aseptic meningitis in a delayed fashion, responded well to steroid administration, but had recurrence of their symptoms. Bovine collagen dural substitutes are resorbed in a process that induces an inflammatory response manifesting with signs of aseptic meningitis and is only alleviated with removal of the dural substitute.

LESSONS

DuraMatrix Suturable, a dural xenograft derived from bovine dermis, though a viable choice for dural repair, is a potential cause of chemical meningitis after duraplasty in Chiari decompression surgery. In patients presenting with delayed and persistent aseptic meningitis after intervention, removal of this dural substitute led to improved symptomatology.

Open access

Predicting clinical outcomes using morphometric changes in adults with complex Chiari malformation undergoing occipitocervical fusion with or without ventral decompression: patient series

John K. Chae, Neelan J. Marianayagam, Ibrahim Hussain, Amanda Cruz, Ali A. Baaj, Roger Härtl, and Jeffrey P. Greenfield

BACKGROUND

The authors assessed the connection between clinical outcomes and morphometrics in patients with complex Chiari malformation (CM) who have undergone posterior fossa decompression (PFD) and subsequent occipitocervical fusion (OCF) with or without ventral decompression (VD).

OBSERVATIONS

The authors retrospectively reviewed 33 patients with CM aged over 21 years who underwent PFD and OCF with or without endoscopic endonasal odontoidectomy at the authors’ institution (21 OCF only and 12 OCF + VD). Clivoaxial angle (CXA), pB-C2 (perpendicular line to the line between the basion and C2), atlantodental interval (ADI), basion-dens interval (BDI), basion-axial interval (BAI), and C1 canal diameter were measured on preoperative and approximately 3-month postoperative computed tomography or magnetic resonance imaging scans. Common symptoms included headache, paresthesia, and bulbar symptoms. Clinical improvement after surgery was observed in 78.8% of patients. CXA, ADI, and BDI all significantly increased after surgery, whereas pB-C2 and BAI significantly decreased. OCF + VD had a significantly more acute CXA and longer pB-C2 preoperatively than OCF only. Patients who clinically improved postoperatively showed the same significant morphometric changes, but those who did not improve showed no significant morphometric changes.

LESSONS

Patients showing improvement had greater corrections in skull base morphometrics than those who did not. Although there are various mutually nonexclusive reasons why certain patients do not improve after surgery, smaller degrees of morphometric correction could play a role.

Open access

Increase in clivo-axial angle is associated with clinical improvement in children undergoing occipitocervical fusion for complex Chiari malformation: patient series

Neelan J. Marianayagam, John K. Chae, Ibrahim Hussain, Amanda Cruz, Ali A. Baaj, Roger Härtl, and Jeffrey P. Greenfield

BACKGROUND

The authors analyzed the pre- and postoperative morphometric properties of pediatric patients with complex Chiari malformation undergoing occipitocervical fusion (OCF) to assess clinical outcomes and morphometric properties that might influence postoperative outcomes.

OBSERVATIONS

The authors retrospectively reviewed 35 patients younger than 22 years with Chiari malformation who underwent posterior fossa decompression and OCF with or without endoscopic endonasal odontoidectomy at their institution (13 with and 22 without odontoidectomy). Clivo-axial angle (CXA), pB-C2, atlantodental interval, basion-dens interval, basion-axial interval, and canal diameter at the level of C1 were measured on preoperative and approximately 3-month postoperative computed tomography or magnetic resonance imaging. The authors further stratified the patient cohort into three age groups and compared the three cohorts. The most common presenting symptoms were headache, neck/shoulder pain, and dysphagia; 80% of the cohort had improved clinical outcomes. CXA increased significantly after surgery. When stratified into those who showed postoperative improvement and those who did not, only the former showed a significant increase in CXA. After age stratification, the significant changes in CXA were observed in the 7- to 13-year-old and 14- to 21-year-old cohorts.

LESSONS

CXA may be the most important morphometric predictor of clinical outcomes after OCF in pediatric patients with complex Chiari malformation.

Open access

Management of failed Chiari decompression and intrasyringeal hemorrhage in Noonan syndrome: illustrative cases

Cody J. Falls, Paul S. Page, Garret P. Greeneway, Daniel K. Resnick, and James A. Stadler III

BACKGROUND

Noonan syndrome (NS) is a rare genetic RASopathy with multisystem implications. The disorder is typically characterized by short stature, distinctive facial features, intellectual disability, developmental delay, chest deformity, and congenital heart disease. NS may be inherited or arise secondary to spontaneous mutations of genes in the Ras/mitogen activated protein kinase signaling pathways.

OBSERVATIONS

Numerous case reports exist detailing the association between NS and Chiari I malformation (CM-I), although this relationship has not been fully established. Patients with NS who present with CM-I requiring operation have shown high rates reoperation for failed decompression. The authors reported two patients with NS, CM-I, and syringomyelia who had prior posterior fossa decompressions without syrinx improvement. Both patients received reoperation with successful outcomes.

LESSONS

The authors highlighted the association between NS and CM-I and raised awareness that patients with these disorders may be at higher risk for failed posterior fossa decompression, necessitating reoperation.