Chiari type 1 malformation in a pseudotumour cerebri patient: is it an acquired or congenital Chiari malformation?

Research process, recap, and prediction of Chiari malformation based on bicentennial history of nomenclature and terms misuse

There is an absent systematic analysis or review that has been conducted to clarify the topic of nomenclature history and terms misuse about Chiari malformations (CMs). We reviewed all reports on terms coined for CMs for rational use and provided their etymology and future development. All literature on the nomenclature of CMs was retrieved and extracted into core terms. Subsequently, keyword analysis, preceding and predicting (2023-2025) compound annual growth rate (CAGR) of each core term, was calculated using a mathematical formula and autoregressive integrated moving average model in Python. Totally 64,527 CM term usage was identified. Of these, 57 original terms were collected and then extracted into 24 core-terms. Seventeen terms have their own featured author keywords, while seven terms are homologous. The preceding CAGR of 24 terms showed significant growth in use for 18 terms, while 13, three, three, and five terms may show sustained growth, remain stable, decline, and rare in usage, respectively, in the future. Previously, owing to intricate nomenclature, Chiari terms were frequently misused, and numerous seemingly novel but worthless even improper terms have emerged. For a very basic neuropathological phenomenon tonsillar herniation by multiple etiology, a mechanism-based nosology seems to be more conducive to future communication than an umbrella eponym. However, a good nomenclature also should encapsulate all characteristics of this condition, but this is lacking in current CM research, as the pathophysiological mechanisms are not elucidated for the majority of CMs.

Bilateral Optic Disk Swelling and Peripheral Visual Field Defects as a Rare Initial Presentation of Primary Chiari I Malformation

Chiari malformation 1 (CM1) is defined as a herniation of encephalon matter through the base of the skull. The amount of herniation is cited as greater than 3 mm or 5 mm, depending on the source of literature. We report a rare case of a 55-year-old male initially presenting with bilateral papilledema and monocular right lower quadrantanopia, found to have CM1. An MRI confirmed 4.87 mm herniation of the cerebellar tonsils at the foramen magnum, and he was diagnosed with CM1. He was later found to have a normal opening pressure on lumbar puncture at 10 cm H₂O. This poses an interesting clinical question as papilledema is defined by elevated intracranial pressure. The ophthalmic defects of this patient with normal intracranial pressure and CM1 are explored in this report.

Population-Based Evaluation of Indirect Signs of Increased Intracranial Pressure

BACKGROUND

The Mayo Clinic Study of Aging (MCSA) is a unique prospective study that systematically evaluates the normal aging population and includes many participants undergoing both MRI and lumbar puncture (LP). Using MCSA date, we aimed to determine the prevalence of indirect signs of raised intracranial pressure (ICP) on MRI and whether these correlate with LP opening pressure (OP). This is a large-scale study that evaluates how often indirect signs of increased ICP occur in a normal population.

METHODS

MCSA participants who had an MRI within 3 months of an LP with recorded OP were included in the study. MRIs were reviewed for indirect signs of raised ICP, including pituitary to sella (P/S) ratio, cerebellar tonsillar ectopia, and optic nerve sheath diameter (ONSD). These signs were evaluated for correlations with OP and influences from body mass index (BMI) and obstructive sleep apnea (OSA).

RESULTS

Five hundred ninety-seven MCSA patients were identified who underwent both LP and MRI. Two hundred sixty (43.6%) were women. The median age was 70.7 years (range 32.6-92.7). Median OP was 152 mm H2O (range 60-314 mm H2O), with 91 (15.2%) participants having an OP ≥ 200 mm H2O. Empty or partially empty sella was seen in 81 (12.8%) of the cohort. The P/S ratio decreased with increasing OP (r = -0.3, P < 0.001). There was a weak correlation between OP and average ONSD (r = 0.184, P = 0.01), which was no longer significant when accounting for age, gender, and BMI (partial r2 = 0.014, P = 0.097). There was no correlation between OP and cerebellar tonsillar ectopia. OSA was associated with increased ONSD (P = 0.004), but this did not remain statistically significant after accounting for age, gender, and BMI (P = 0.085).

CONCLUSION

Smaller pituitary gland size correlated with increasing OP. This suggests that ICP is a continuum with some normal individuals demonstrating asymptomatic radiologic signs of raised ICP.

Unexpected Progression of Tonsillar Herniation in Two Pediatric Cases with Chiari Malformation Type I and Review of the Literature

BACKGROUND

Chiari malformation type 1 (CM-1) is a generally congenital, rarely acquired disease characterized with 5 mm or more displacement of cerebellar tonsils through foramen magnum.

METHODS

Here, we report about 2 patients with CM-1 progressed in the degree of tonsillar herniation from our clinic, whereas increasing in prolapse of tonsillar herniation after diagnosis is extremely uncommon.

RESULTS

The first patient aged 17 years was diagnosed with CM-1 in 2009 and was operated due to progression of 5 mm radiologically and worsening symptoms in 2014. The second 5-month-old patient initially showed just low-settled tonsillar localization at the borderline, then it descended by 2 cm when the patient reached 3 years of age, yet could not be operated because of parents' objection.

CONCLUSION

Due to lack of reports on increasing tonsillar descent in the literature, these case reports will contribute to natural history and management of CM-1.

Cervico-medullary compression ratio: A novel radiological parameter correlating with clinical severity in Chiari type 1 malformation

OBJECTIVES

Chiari malformation type 1 (CM-1) is associated with cough headache, intracranial hypertension, cerebellar and spinal cord symptoms/signs. Herniated cerebellar tonsil length (HCTL) is widely used radiological parameter to determine the severity of CM-1, but with limited utility due to its weak correlation with some clinico-radiological findings. In this study, we aimed to evaluate a novel, practical parameter (cervico-medullary compression ratio; "CMCR") for its relationship with clinico-radiological findings in CM-1.

PATIENTS AND METHODS

Thirty-five adult patients (17 F, 18 M) with CM-1 were included in this retrospective study. Head CT and craniospinal MR images were assessed. CMCR was calculated as the ratio of herniated cerebellar tonsil surface area to foramen magnum surface area, and HCTL was measured. These two parameters were correlated with clinical and radiological findings.

RESULTS

The mean CMCR was 0.60 ± 0.15 and mean HCTL was 8.91 ± 3.4 mm with no significant difference between gender and age groups for both parameters. For cough headache (0.64 ± 0.14 vs 0.52 ± 0.15, p = 0.043) and syringomyelia (0.67 ± 0.11 vs 0.56 ± 0.16, p = 0.039), only CMCR; for intracranial hypertension (CMCR: 0.64 ± 0.14 vs 0.55 ± 0.16, p = 0.049; HCTL: 9.66 ± 3.59 mm vs 7.79 ± 3.03 mm; p = 0.045) and cerebellar symptoms (CMCR: 0.65 ± 0.14 vs 0.54 ± 0.16, p = 0.048; HCTL: 10.4 ± 3.5 mm vs 7.4 ± 2.8 mm, p = 0.041), both CMCR and HTCL were significantly different between patients with and without respective findings. However, neither CMCR nor HTCL was different between patients with and without spinal cord symptoms and hydrocephalus.

CONCLUSION

CMCR is a superior numerical parameter than HCTL for the assessment of clinical severity in CM-1 cases and needs further validation with larger studies.

The Significance and Reliability of Imaging Findings in Pseudotumor Cerebri

The objective of our study was to provide a comparative assessment of previously reported magnetic resonance imaging (MRI) parameters in primary and secondary pseudotumor cerebri (PTC) patients, to examine their diagnostic contribution, and to evaluate their association with symptoms, neuro-ophthalmological findings, laboratory results, and cerebrospinal fluid characteristics. Twenty-eight consecutive patients with PTC were included in the study. Age- and sex-matched 20 individuals with normal neurologic examination served as the control group. Modified Dandy Criteria were used for the diagnosis of PTC. Orbital and cranial MRI and MR venography of all patients and controls were assessed by three radiologists. According to our study, posterior flattening of the globe (64% sensitive, 100% specific), optic nerve sheath distention (46% sensitive, 100% specific), vertical tortuosity of the optic nerve (30% sensitive, 95% specific), and partial empty sella (43% sensitive, 100% specific) emerged as particularly valuable markers for a diagnosis of PTC.

Cranial morcellation decompression for refractory idiopathic intracranial hypertension in children

BACKGROUND

Primary idiopathic intracranial hypertension (PIIH) in children is rare and has a poorly understood pathophysiology. It is characterized by raised intracranial pressure (ICP) in the absence of an identified brain lesion. Diagnosis is usually confirmed by the measurement of a high cerebrospinal fluid (CSF) opening pressure and exclusion of secondary causes of intracranial hypertension. Refractory PIIH may lead to severe visual impairment. The purpose of this study was to evaluate a cranial morcellation decompression (CMD) technique as a new surgical alternative to stabilize intracranial pressure in PIIH.

MATERIALS AND METHODS

A literature review was carried out, disclosing only 7 pediatric cases of PIIH treated with surgical skull expansion. In addition, we describe here one case of our own experience treated by CMD.

CONCLUSIONS

CMD surgery is a safe and effective option to control refractory PIIH in selected patients.

Chiari malformation and tuberculous meningitis: aetiology and management

This is the first reported case of a Chiari 1 malformation in association with tuberculous (TB) meningitis. We present a case of a 23-year-old woman with a 2-week history nocturnal fever, vertigo, headache and projectile vomiting. She had nystagmus, scanning speech, bilateral papilloedema and ataxia. Cranial imaging showed a 10 mm tonsillar herniation. Posterior fossa decompression was done. Because the patient's gamut of symptoms was highly suspicious for a central nervous system infection, a lumbar tap was done which revealed TB meningitis. Four years later, after anti-TB medications and rehabilitation, all her symptoms except gait instability resolved.

Chiari Type 1 Malformation-induced Intracranial Hypertension with Diffuse Brain Edema Treated with Foramen Magnum Decompression: A Case Report

Chiari type 1 malformation (CM1) rarely causes papilloedema, which is indicative of high intracranial pressure with or without ventricular dilatation. Furthermore, concomitant brain parenchymal abnormalities have not been reported to date. In this paper, the authors report on a young woman of CM1-induced intracranial hypertension (ICH) with diffuse brain edema with a focus on venous sinus assessment, and discuss the surgical strategy. A 24-year-old woman presented to Nagoya University Hospital complaining of 4-year history of severe occipital headache and blurry vision with slowly progressive worsening. Head and whole spine MRI showed a CM1 with diffuse white matter hyperintensities (WMH) on T2-weighted imaging and narrowed brain sulci without hydrocephalus. Lumbar puncture revealed extremely high opening pressure. Detailed blood examination and other radiographical imaging studies denied the presence of tumor, collagen disease, encephalitis and other entities. Head magnetic resonance venography and angiography demonstrated severe transverse sinus stenosis on both sides. Foramen magnum decompression was performed to alleviate the ICH by restoration of cerebrospinal fluid (CSF) stagnation at the foramen magnum with successful outcome. The patient completely recovered from preoperative symptoms immediately after surgery. The diffuse WMH and narrowing brain sulci have been resolving. The most feasible explanation for this complicated pathophysiology was ICH induced by CM1 led to transverse sinus collapse, resulting in diffuse WMH as a result of venous hypertension. This case report is the first illustration of successful surgical treatment of CM1 with diffuse brain edema with a focus on venous sinus assessment.