Dural substitutes have emerged as favorable alternatives to autologous grafts. This shift in approach is evident in the growing use of sutureless grafts (e.g., DuraGen) over traditional sutured options (e.g., bovine pericardial patch). This study was conducted to gain insights into the choice between the two in terms of the rate of postoperative complications. This prospective study was conducted between May 15, 2023 and January 31, 2024 at a tertiary-care government hospital in India. The patients received sutured (bovine pericardial patch) or sutureless (DuraGen patch) dural substitutes. Success in both groups was defined by the absence of postoperative complications. Wound healing was evaluated on postoperative day (POD) 3, 10, and 14. Follow-up assessments occurred at 1 and 3 months. Cerebrospinal fluid pooling was assessed by computed tomography (immediately after surgery and on POD 10) and brain magnetic resonance imaging (after 1 month). A total of 50 patients received sutured (bovine pericardial patch; n = 25) or sutureless (DuraGen patch; n = 25) dural substitutes to repair the dural defect that occurred after resection of cranial (62%) and spinal (20%) tumors. The bovine pericardial patch application was successful in 21 patients (84.0%), whereas the DuraGen patch application was successful in 23 patients (92.0%). The success rates with the bovine pericardial patch were 100% in patients with spinal tumors and patients who underwent foramen magnum decompression, 33.3% in patients with meningocele myelocystocele, and 81.8% in patients with cranial tumors. The success rates with the DuraGen patch were 80% in patients with spinal tumors and 95% in patients with cranial tumors. Sutureless grafts like DuraGen offer rapid application, reduced infection risk, and suitability for complex areas like the skull base. Sutured grafts may be preferred for larger defects due to their adaptability and inherent strength.

Pediatric complex Chiari I Malformation (CCM), defined by Chiari I with additional craniovertebral junction anomalies, has been associated with higher failure rates following foramen magnum decompression (FMD) alone, leading some to advocate occipitocervical fixation (OCF) or ventral decompression. This study evaluates a single-institution experience with isolated FMD in CCM. Patients meeting CCM criteria were identified from a prospective surgical database from March 2020 to December 2023. Patients with incomplete imaging or < 6-month follow-up were excluded. Pre- and postoperative imaging assessed tonsillar descent, brainstem crowding, CSF flow, and syringomyelia. Clinical outcome was recorded. Sixty patients met the inclusion criteria for CCM, but nineteen patients were excluded. Forty-one CCM patients underwent FMD. Headache prevalence decreased from 73.2% preoperatively to 7.3% at last follow-up (p < 0.001). One patient (2.4%) required reoperation for inadequate decompression. Median tonsillar descent improved from 15.0 to 0.0mm (p < 0.001), and obex ectopia from 7.0 to 0.0mm (p < 0.001). Anterior and posterior CSF effacement significantly improved. Craniocervical angle increased from 122.0 to 130.0° (p = 0.007), and pb-C2 distance decreased from 7.0 to 5.0mm (p < 0.001). No patient required OCF or ventral decompression during a mean 2.1-year follow-up. Isolated FMD provides effective clinical and radiological improvement in most pediatric CCM patients. Routine addition of OCF or ventral decompression may be unnecessary, preserving cervical mobility while minimizing morbidity.

Achondroplasia (ACH) results from a missense mutation in the FGFR3 (fibroblast growth factor receptor 3) gene, representing the primary cause of short stature in humans. This study aims to describe the clinical features, complications, and management outcomes of Saudi patients with achondroplasia. This retrospective study included achondroplasia cases followed at the endocrinology clinic at King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia, from (2015-2025). Thirty-three patients were included; 32 were heterozygous and one was homozygous for the FGFR3 c.1138G > A variant. Median age at presentation was 24 months (IQR 7-60), and 54.5% were male. Short stature was universal, with frontal bossing and skeletal deformities present in 93.9%. Developmental delay was observed in 54.5%, while neurological symptoms and hearing loss were each noted in 42.4%. Clinical suspicion of obstructive sleep apnea (OSA) was identified in 17/33 patients (51.5%), with 41.2% (7/17) requiring surgical intervention. Yet, polysomnography was performed in only 10 patients and confirmed OSA in all cases. Radiologic abnormalities were common, with abnormal brain or spine imaging in 96.4% (27/28), foramen magnum stenosis in 50% (14/28), and spinal abnormalities in 71.4% (20/28). Median baseline height SDS was - 5.5. Growth hormone therapy was used in four patients, with only one demonstrating transient benefit. Overall mortality was 9.1% (3/33), including one homozygous infant and two heterozygous patients. This study provides the largest single-center characterization of achondroplasia in Saudi Arabia. The findings highlight the high burden of airway and hearing complications and the limited long-term efficacy of GH therapy, underscoring the need for multidisciplinary and targeted management strategies.

Cerebrospinal fluid (CSF) flow oscillations have emerged as a potentially important marker related to brain clearance, but their acquisition often relies on specialized imaging MRI sequences. The purpose of this work was to enable quantitative assessment of CSF flow associated with cardiac, respiratory, and low-frequency cycles using widely available functional magnetic resonance imaging (fMRI) acquisitions. A method was developed to translate fMRI-derived CSF inflow signals into quantitative flow rates. This approach modeled the spin-history of an oscillating ensemble of molecules. Validation was performed using phantom experiments with cardiac-, respiratory-, and low-frequency-like oscillatory flow. The method was further applied to resting-state data from 48 older adults (68-82 years, 19 women) to characterize CSF flow at the foramen magnum. Phantom experiments demonstrated excellent correlations between estimated and true velocities for cardiac- and respiratory-like frequencies (r = 0.94 and 0.97, respectively) and moderate correlation for the low-frequency-like oscillation (r = 0.58). In the population cohort, median CSF stroke volumes were 0.77 [0.57, 1.09] mL for the cardiac cycle, 0.38 [0.26, 0.88] mL for the respiratory cycle, and 0.26 [0.14, 0.39] mL for the low-frequency cycle. The proposed spin-history modeling method enabled quantitative estimation of CSF flow components using a conventional fMRI dataset and showed that the cardiac cycle dominates CSF motion at the foramen magnum.

Treatment of fusiform vertebral artery aneurysms is demanding because meticulous preservation of perforators and the PICA is required. The occipital artery is mapped with Doppler and harvested by incising the overlying muscle, allowing en-bloc elevation of the musculature. Accurate burr-hole placement minimizes venous sinus injury and reduces the bony defect, while early opening of the foramen magnum improves anatomical orientation and facilitates the bypass technique. The extracranial vertebral artery is safely identified with Doppler before performing OA-PICA bypass and subsequent trapping. Standardized steps improve technical reliability and enhance clinical outcomes.

Spontaneous intracranial hypotension can be caused by CSF leakage into the epidural space. Dynamic CTM in the prone Trendelenburg position is highly sensitive for the detection of ventral dural tears, but we have observed reduced effectiveness at the thoracolumbar junction with steep pelvic elevation, which might be related to a reduced subarachnoid pressure in lower levels in this position. The purpose of this study was to compare the conspicuity of ventral leaks across spinal levels and to assess the relationship between leak conspicuity and the degree of pelvic elevation. We conducted a single-center retrospective cohort of patients with SIH and confirmed ventral spinal CSF leaks who underwent dCTM. All patients underwent CTM in prone Trendelenburg position. An additional acquisition in the neutral position and without additional contrast was obtained selectively when the initial Trendelenburg acquisition was negative or equivocal. Examinations in which the leak became definite only on imaging obtained in the neutral position were classified as Trendelenburg false-negative. TFN frequency was analyzed according to spinal level and the relative height of the leak site with respect to the foramen magnum in the examination position. Of 47 examinations, 43 met the inclusion criteria and were confirmed to have well-localized ventral CSF leaks. TFN occurred in 5/43 examinations and was observed exclusively at lower thoracic levels and the thoracolumbar junction (T11-T12 and T12-L1 levels), with no TFN identified at more cranial levels. When leak levels were dichotomized as above or at/below T11-T12, TFN occurred in 0/35 versus 5/8 examinations, respectively (Fisher test p < .001). The vertical height of the leak site during the examination was associated with TFN occurrence, even within the subgroup of low-level leaks. Trendelenburg prone dCTM demonstrated a reproducible, level-dependent visualization pattern, with false-negatives clustering at lower thoracic levels and the thoracolumbar junction, particularly at steep hip elevations. These findings support the role of subarachnoid pressure in ventral leak conspicuity on CTM. When a ventral leak is suspected and the Trendelenburg acquisition is negative or equivocal, adding a neutral acquisition may improve leak visualization and localization at the thoracolumbar junction.

Bow hunter's syndrome (BHS) occurs when physiological head rotation or extension leads to dynamic vertebral artery (VA) occlusion and transient vertebrobasilar insufficiency. Most cases are due to degenerative compression at the V2-V3 segments. Tumor-related BHS is exceedingly rare, and to date, compression of the intradural V4 segment by a neoplasm has not been reported. A 77-year-old male developed episodic right-sided weakness, hemisensory loss, and dizziness that recurred reliably with leftward head rotation and resolved immediately on returning to a neutral position. MRI demonstrated a homogeneously enhancing intradural extramedullary mass at the left foramen magnum displacing the VA and compressing the cervicomedullary junction. The patient underwent midline suboccipital craniotomy, C1 laminectomy, and partial occipital condylectomy for microsurgical resection. Gross-total removal was achieved, decompressing the V4 segment and restoring normal vascular caliber. Pathology confirmed a grade I meningioma. All positional symptoms resolved postoperatively, and postoperative MRI showed no residual tumor. This case represents the first documented instance of BHS caused by tumor-related V4 compression. It underscores the importance of considering intracranial lesions in patients with reproducible, position-dependent vertebrobasilar symptoms and highlights resection as curative therapy when vascular compromise arises from space-occupying pathology. https://thejns.org/doi/10.3171/CASE25833.

Isolated bilateral lambdoid and sagittal synostosis (iBLSS) has been of particular interest as a special entity and is commonly associated with hydrocephalus and Chiari malformation type I (CM-I). The authors present the case of a 5-month-old female diagnosed with iBLSS, complicated by hydrocephalus and CM-I, and review the available literature. At 5.5 months of age, the child underwent endoscopic release of the fused sagittal and bilateral lambdoid sutures. Follow-up at 5 years of age showed significant craniofacial improvement and resolution of the hydrocephalus and CM-I, which has not been previously reported in the literature. Literature review included 95 cases, with the most common association being CM-I, followed by hydrocephalus and increased intracranial pressure. The majority of patients underwent cranial vault release with or without foramen magnum decompression. Endoscopic release is an effective approach for managing iBLSS and led to the resolution of hydrocephalus and CM-I in the present case. https://thejns.org/doi/10.3171/CASE251019.

Vertebral artery (VA) anomalies, particularly those associated with congenital atlantoaxial dislocations, are well documented in the literature. Typically, these anomalies are linked to persistent first intersegmental artery variants or occur in conjunction with occipitalization of the atlas. The case presented in this report is unique due to the presence of bilateral ectatic VAs with an anomalous course beneath the posterior arch of C1, in the absence of occipitalization of the atlas. This finding adds to the growing recognition of anatomical variability in patients with congenital conditions such as os odontoideum and Klippel-Feil syndrome (KFS). The authors present the case of a 65-year-old female patient with progressive cervical myelopathy, os odontoideum, and KFS. The preoperative imaging revealed the VA anomalies, and additional caution was exercised intraoperatively. The patient underwent C1-4 fixation and foramen magnum decompression using robot-assisted cervical fusion and neuronavigation. In patients with fused cervical segments, VA anomalies may be overlooked in preoperative imaging, highlighting the need for intraoperative vigilance. Robot-assisted surgery and neurophysiological monitoring significantly improve the safety and precision of the procedure, ensuring optimal outcomes in complex cases like this. https://thejns.org/doi/10.3171/CASE25493.

Gamma knife radiosurgical technique and clinical outcomes for C1-C4 cervical spine lesions: A decade-long experience.

Introduction: Computed Tomography (CT) brain imaging provides high-resolution anatomical detail but involves relatively higher radiation doses, necessitating dose monitoring and optimisation. Diagnostic reference levels (DRLs) are recommended dose indicators for optimising radiation exposure without compromising diagnostic image quality; however, national DRLs for CT brain imaging have not yet been established in South Africa. This article presents a protocol for establishing local DRLs for non-contrast- (non-CE) and contrast-enhanced (CE) adult CT brain examinations at an academic hospital in Johannesburg, South Africa. Materials and Methods: The research site is at a single hospital in Johannesburg, South Africa. The research design for this study is retrospective. A sample of 197 adult CT brain examinations (63 non-CE, 34 CE, and 100 combined non-CE and CE examinations) performed between 1 January and 31 December 2024 will be used to develop local DRLs. The 64-slice CT scanner of choice for data collection is the Siemens SOMATOM Definition AS. The population defined for this study is individuals aged 18–70 years. The preferred contrast media used for CT brain examination at the research site is 40 mL of Omnipaque 350. The scan range for CT brain is from the base of the skull (foramen magnum) to the vertex, ensuring full coverage of intracranial structures. Dose metrics, including the volumetric CT dose index (CTDIvol) and dose–length product (DLP), will be extracted from archived dose reports. Local DRLs will be established as the 75th percentile values of CTDIvol and DLP for each protocol group. Descriptive statistics (mean, median, and interquartile range) will be used to summarise the data demographics. The effective dose will be estimated by applying a head-specific conversion coefficient to the DLP values. Results: As this is a study protocol, results are not yet available. Local DRLs will be reported as the mean, median, and 75th percentile values of the DLP and CTDIvol for non-CE, CE, and for both non-CE and CE CT brain examinations. The effective dose will be estimated by applying a head-specific dose conversion coefficient (k-factor) to the mean DLP values. Expected Outcomes: This study is expected to establish local DRLs for adult CT brain examinations, providing baseline data for dose optimisation and supporting the future development of national DRLs in South Africa. Conclusions: Establishing local DRLs will support the optimisation of the radiation dose in CT brain imaging to keep the dose as low as reasonably achievable. The DRLs developed for this study will contribute to national and international efforts toward optimising radiation dose during diagnostic X-ray imaging investigations.

Background: Chiari malformation (type 1) is a rare condition in which the cerebellar tonsils descend through the foramen magnum into the spinal canal. This in turn leads to compression of the spinal cord at foramen magnum interfering with the flow of cerebrospinal fluid leading to craniospinal dissociation and as a result hydrocephalus and syringomyelia. Sometimes it occurs secondary to space occupying lesions in intracranial compartments.

Abstract The foramen magnum (FM) is a critical structure at the craniovertebral junction (CVJ), influencing surgical access, radiological evaluation, and forensic sex estimation. Although international reference values exist, computed tomography (CT) based FM morphometry remains underreported in the Pakistani population. This study provides population-specific high-resolution computed tomography (HRCT) measurements, evaluates gender and age-related variation, and classifies FM shape using the Martin and Saller index. A retrospective analysis of 166 adult HRCT scans (78 males, 88 females; age: 18–87 years) was conducted using 1.0-mm axial bone-window images on the Vitrea workstation. Measurements included anteroposterior diameter (APD), transverse diameter (TD), FM index (FMI), and FM area (FMA). FM shape was categorized into narrow (≤81.9%), medium (82–85.9%), and large (≥86%). Data were analyzed using descriptive statistics, ANOVA, and Pearson's correlation. Males exhibited consistently larger FM dimensions than females across all age decades. TD, FMA, and FMI showed similar gender-based dimorphism. The most frequent FM shape in both genders was narrow, with 52.3% incidence in females and 41% in males (p = 0.345). FM shape varied significantly across age groups (p = 0.018). Two-way ANOVA demonstrated significant age effects on APD (p = 0.023), gender effects on TD (p &lt; 0.001), and FMI (p = 0.016). APD and TD strongly correlated with FMA (r = 0.848 and r = 0.835), while FMI negatively correlated with FMA(r = −0.353) This study establishes HRCT-based FM reference values for a Pakistani adult subpopulation, demonstrating gender dimorphism, age-related variation in APD and FM indices, and a predominance of the narrow FM shape. These findings support neurosurgical planning, radiological interpretation, and forensic applications within the Pakistani setting.

While neurosurgical posterior fossa decompression with duraplasty (PFDD) may provide clinical and radiological improvement for Chiari malformation-I (CM-I)-syringomyelia, the comparative efficacy and safety of PFDD without vs with intradural tonsillar manipulation (posterior fossa decompression with tonsil resection) has remained controversial for over 5 decades. We conducted a retrospective cohort study of 1231 CM-I-syringomyelia patients treated at our institution from 2003 to 2024, comparing 2 techniques: standard PFDD and foramen magnum and foramen of magendie dredging (FMMD, a modified posterior fossa decompression with tonsil resection procedure). Propensity score matching was used to balance baseline characteristics between the 2 groups. The primary outcomes were syrinx regression >50%, while secondary outcomes encompassed symptom-related parameters, syrinx regression, complication-related parameters, and reoperation rate. A total of 1231 patients with CM-I were included, of whom 310 (25.2%) were in the PFDD group, and 921 (74.8%) were in the FMMD group. Per treatment analysis demonstrated no increase in odds of complications for FMMD (P > .05). PFDD was noninferior to FMMD in clinical improvement and syrinx regression (P = .147, P = .169, respectively). Syrinx regression (>50% reduction) was superior following FMMD (78% vs 60%, P < .001). PFDD had a higher rate of revision surgery than FMMD (15.5% vs 4.1%, log-rank P < .001). At our center, FMMD demonstrated greater effectiveness in managing syringomyelia, with higher rates of syrinx regression (>50% reduction), a lower rate of revision surgery, and no increase in complications compared with PFDD. Nonetheless, PFDD was similar to FMMD regarding clinical improvement and syrinx regression.

This case series describes two patients with severe Crouzon syndrome and persistent Chiari I malformation. Initial treatment with standard posterior vault distraction osteogenesis and frontoorbital advancement failed to resolve the patient's symptoms. One patient developed severe syringomyelia and myelopathy refractory even to standard suboccipital decompression. Given the persistent posterior fossa constriction, an en-bloc posterior vault distraction incorporating the foramen magnum was performed over 21 days, achieving an expansion of 20mm. This approach resulted in complete symptom resolution in both patients, disappearance of syringomyelia, and normalization of posterior fossa anatomy. One procedure was guided by intraoperative cone-beam CT (Brainlab Loop-X) to optimize the distraction vector and ensure optimal ventricular catheter placement during the concomitant shunt revision. These are the first reported cases of en-bloc posterior vault distractions incorporating the foramen magnum to simultaneously address both posterior cranial restriction and secondary Chiari I malformation. They proof the feasibility of a mono-bloc technique to simultaneously distract the posterior cranial vault and the posterior fossa down to the foramen magnum.

T2 hyperintensity on fetal brain MRI is frequently observed in fetuses with an open neural tube defect (ONTD) and may reflect edema, impaired CSF circulation, or altered brain maturation. By characterizing the diffusion of water molecules within brain tissue, DWI may help differentiate among these etiologies by assessing water diffusion as a marker of brain microstructure. Our aim was to investigate the relationship between brain T2-hyperintensity and ADC values in fetuses following prenatal ONTD repair. We retrospectively analyzed fetal MRI scans performed 6 weeks after in utero ONTD repair at a single center. T2 hyperintensity was defined as a region with signal intensity subjectively higher than that of the surrounding brain parenchyma. ADC values were measured in the frontal, temporal, parietal, and occipital lobes on axial brain DWI sequences (b=700 s/mm2). Hindbrain herniation was evaluated, and reversal was defined when the cerebellum was seen above the foramen magnum. ADC values were compared between fetuses with and without T2 hyperintensity using the Mann-Whitney U test. A P value < .05 was considered significant. Forty-nine fetuses underwent repair at 25.0 [23.3-26.4] weeks. During the postoperative MRI at 31.2 [29.9-33.3] weeks, T2 hyperintensity was seen in 35/49 (71.4%) fetuses. ADC values were lower in most studied brain regions in fetuses with T2 hyperintensity compared with their counterparts without T2 hyperintensity (right parietal lobe: 2.68 [1.38-7.82] ×10-6 mm2/s versus 3.36 [2.32-7.05] ×10-6 mm2/s, P = .02; left parietal lobe: 2.80 [1.40-7.38] versus 3.45 [1.81-7.58] ×10-6 mm2/s, P = .03; right temporal lobe: 2.75 [1.41-6.63] versus 3.53 [1.87-7.58] ×10-6 mm2/s, P <.01; right occipital lobe: 3.19 [1.20-7.86] versus 4.30 [2.18-7.18], P = .04). Complete hindbrain herniation reversal was more common in those without T2 hyperintensity (100% versus 65.7%, P < .01). After prenatal ONTD repair, the presence of T2 hyperintensity was associated with lower ADC values in most examined brain regions, suggesting altered brain microstructure or delayed myelination.

Anti-neutrophil cytoplasmic antibody-associated vasculitis (AAV) is a group of small-vessel necrotizing vasculitides with minimal immune complex deposition. Hypertrophic cranial pachymeningitis, a rare complication of AAV, is characterized by focal/diffuse dural thickening and fibrosis, causing neurological dysfunction such as headache and optic nerve injury. While AAV-associated hypertrophic cranial pachymeningitis is well documented, reports of concurrent spinal dural involvement remain scarce. This case highlights the rare co-occurrence of cranial and spinal dural involvement in AAV, providing new clinical evidence to expand the understanding of AAV-related dural manifestations and improve diagnostic awareness among clinicians. A 57-year-old male presented with fever, headache, otalgia, and hearing loss, and was diagnosed with granulomatosis with polyangiitis based on positive anti-proteinase 3 antibodies (664.3), cytoplasmic anti-neutrophil cytoplasmic antibody (1:10). Symptoms resolved with glucocorticoids, disease-modifying antirheumatic drugs, and anti-infective therapy. He later developed recurrent headache and lumbodorsal pain. Thoracic magnetic resonance imaging (MRI) revealed a T10 to 12 epidural lesion, which was surgically resected. Pathology confirmed epidural vasculitis with necrotic/fibrous tissue, granulation, and inflammatory cell infiltration. Methylprednisolone and cyclophosphamide relieved back pain, but headaches persisted. Cranial MRI showed dural thickening in the cerebellar, posterior fossa, and foramen magnum regions, consistent with pachymeningitis. Cerebrospinal fluid analysis showed elevated mononuclear cells (35.00 × 106/L), nucleated cells (40.00 × 106/L), and protein (1.49 g/L), with negative cultures. The final diagnosis was granulomatosis with polyangiitis complicated by concurrent cranial and spinal dural involvement. Initial management included glucocorticoids, disease-modifying antirheumatic drugs, and anti-infective therapy, which resolved the patient's fever, otalgia, and hearing loss. Surgical resection was performed for the T10 to 12 epidural lesion, followed by immunosuppressive therapy with methylprednisolone and cyclophosphamide. After adjustment of the treatment regimen, the patient's headache improved. Initial therapy resolved the patient's fever, otalgia, and hearing loss. Surgical resection combined with immunosuppressive therapy relieved lumbodorsal pain but failed to resolve headaches initially; cranial MRI confirmed pachymeningitis, and cerebrospinal fluid analysis indicated inflammatory changes. After adjustment of the treatment regimen, the patient's headache improved, and he has remained clinically stable during follow-up. This case demonstrates that AAV can involve both cranial and spinal dura mater. Clinicians should consider dural involvement in AAV patients presenting with lumbodorsal pain.

Secondary Chiari-like formation (SCLF) is an acquired herniation of the cerebellar tonsils through the foramen magnum, typically resulting from a craniospinal pressure gradient or reduced posterior fossa volume. We report a rare case of SCLF caused by massive bone overgrowth after occipitocervical fixation (OCF) in a child. An 8-year-old boy with Klippel-Feil syndrome and basilar invagination developed quadriparesis after OCF. His symptoms worsened following repeat OCF performed due to misdiagnosis. Four months later, the quadriparesis progressed further. Serial imaging demonstrated foramen magnum crowding caused by a hypertrophic graft, along with cerebellar tonsillar herniation. Foramen magnum decompression, performed 10months after the second surgery, led to rapid motor improvement, allowing independent ambulation within 3weeks. This case highlights massive graft overgrowth as a unique mechanical etiology of SCLF. Vigilance and careful comparison of serial craniovertebral junction imaging are crucial in pediatric patients with neurological deterioration after OCF.

Condylar screws have broadened fixation options for Craniocervical Fusion techniques and are used when occipital squama anchorage is inadequate. They may also outperform barplate constructs in patients with connective tissue disorders. The condyles are entirely dissected, sacrificing the Posterior Condylar Emissary Vein. An entry 3mm lateral to the foramen magnum is created. Hand drilling converges20° medially, aiming toward the basion underfluoroscopy, under continuous hypoglossal EMG monitoring. A 34-mm lag screw is inserted and confirmed by intraoperative CT. Condylar screws provide reliable fixation and are a useful adjunct to contemporary CCF techniques.

We investigated the association between Chiari-I-Malformation (CM1) and all types of lambdoid-involved craniosynostosis, aiming to distinguish the impact of suture fusion from underlying diagnosis. We conducted a retrospective cohort study of lambdoid craniosynostosis patients born between 2000 and 2024. Patients were classified as clinically non-syndromic or syndromic, the later subdivided into 'known craniosynostosis syndromes' (e.g., Crouzon/Pfeiffer, Apert), 'syndromic other' (e.g., ZIC1, HUWE-1), and clinically syndromic (without known mutation). Of 2341 patients with craniosynostosis, 133 had lambdoid involvement: 22 had isolated unilambdoid synostosis (11 non-syndromic, 11 syndromic), 4 had isolated bilambdoid synostosis (all syndromic), and 107 had multisuture synostosis (13 non-syndromic, 94 syndromic). All but 17 underwent early vault expansion; foramen magnum decompression was not routinely performed.CM1 occurred in 2/22 (9%) with isolated unilambdoid synostosis, 9/23 (39%) with multisuture synostosis with unilambdoid involvement, and 38/88 (43%) with bilambdoid involvement.Among multisuture cases, CM1 developed in 6/10 clinically syndromic, 6/12 'syndromic other', 6/13 non-syndromic, and 29/69 (42%) known craniosynostosis syndromes (including 23/49 (47%) Crouzon/Pfeiffer).Ultimately, 12/49 (24%) CM1-patients received CM1-associated surgery (2 clinically syndromic, 8 Crouzon/Pfeiffer, 2 'syndromic other'). Baseline MRI for CM1 screening appears not indicated in unisutural unilambdoid synostosis, regardless of syndromic diagnosis. Baseline MRI seems indicated for all multisuture cases with lambdoid involvement. Follow-up imaging may be limited to symptomatic patients, provided routine consultation with counseling on warning signs is done. The need for CM1-associated surgery appears more related to the underlying diagnosis than to the lambdoid fusion's impact on skull growth alone.