Foramen magnum decompression without bone removal: C1–C2 posterior fixation for Chiari with congenital atlantoaxial dislocation/basilar invagination

Background: Atlantoaxial dislocation (AAD) and basilar invagination (BI) may coexist with Chiari malformations (CM) and a small posterior fossa volume. These are typically treated with craniovertebral junction fusion and foramen magnum decompression (FMD). Here, we evaluated whether C1–C2 posterior reduction and fixation (which possibly opens up the ventral foramen magnum) would effectively treat AAD and CM without additionally performing FMD. Methods: This is a retrospective analysis of 38 patients with BI, AAD, and CM who underwent C1–C2 posterior reduction and fusion without FMD. Baseline and follow-up clinical, demographic, and radiological data were evaluated. Results: The vast majority of patients (91.9%) improved both clinically and radiographically following C1–C2 fixation alone; none later required direct FMD. Notably, AAD was irreducible in 25 (65.8%) patients. Preoperatively, syringomyelia was present in 28 (73.7%) patients and showed resolution. In 3 (8.1%) patients, resolution of syrinxes did not translate into clinical improvement. Of interest, 5 patients who sustained inadvertent dural lacerations exhibited transient postoperative neurological worsening. Conclusions: Posterior C1–C2 distraction and fusion alone effectively treated AAD, BI, accompanied by CM. The procedure sufficiently distracted the dens, reversed dural tenting, and restored the posterior fossa volume while relieving ventral brainstem compression making FMD unnecessary. Surgeons should, however, be aware that inadvertent dural lacerations might contribute to unwanted neurological deterioration.

Improvement of Hydrocephalus in Patients with Chiari Malformation After Posterior Fossa Decompression

Introduction. The association between hydrocephalus and Chiari malformation (CM) has not been described frequently. Ventricular dilation affects 7% to 10% of patients with CM, but the ideal choice of surgical treatment is controversial. Wereport a case of a patient with Chiari malformation and hydrocephalus with improvement in clinical symptoms and ventricular dilatation. Case Description. A 19-year-old male complaining of frontal headache when coughing, laughing and during valsalva maneuvers, associated with dizziness for 2 months. Magnetic resonance (MR) showed hydrocephalus and small posterior fossa with overcrowding of contents, characterizing Chiari malformation type I, with cerebellar tonsils protruding through magnum foramen. Patient underwent surgery with posterior fossa decompression in a semi-sitting position and removal of the arc C1.After 3 months of follow-up, headache disappeared becoming asymptomatic. Control MR showed improvement of hydrocephalus with restoration of the cisterna magna and CSF flow. Discussion. Hydrocephalus has been related to CM for a long time. In our case, we performed treatment with intradural and intra-arachnoidal approach with bilateral tonsillectomy without placing ventricular shunt. The cisterna magna was “recreated”. There was improvement of hydrocephalus with decreased Evans ratio index and symptoms disappearance. Although there is no other studies addressing such matter, in this case, the improvement suggests that the CSF compression at the foramen magnum was the cause of associated hydrocephalus with Chiari malformation.

Contiguous triple spinal dysraphism associated with Chiari malformation Type II and hydrocephalus: an embryological conundrum between the unified theory of Pang and the unified theory of McLone

Triple spinal dysraphism is extremely rare. There are published reports of multiple discrete neural tube defects with intervening normal segments that are explained by the multisite closure theory of primary neurulation, having an association with Chiari malformation Type II consistent with the unified theory of McLone. The authors report on a 1-year-old child with contiguous myelomeningocele and lipomyelomeningocele centered on Type I split cord malformation with Chiari malformation Type II and hydrocephalus. This composite anomaly is probably due to select abnormalities of the neurenteric canal during gastrulation, with a contiguous cascading impact on both dysjunction of the neural tube and closure of the neuropore, resulting in a small posterior fossa, probably bringing the unified theory of McLone closer to the unified theory of Pang.

Fluid Area Measurements in the Posterior Fossa at 11-13 Weeks in Normal Fetuses and Fetuses with Open Spina Bifida

Objectives: To measure the area of the intracranial translucency (IT) (syn: 4th ventricle) and the future cisterna magna (CM) in normal fetuses and to compare with fetuses with open spina bifida. Patients: In the midsagittal plane of the face of 220 fetuses between 11 and 13 weeks' gestation, the areas of the IT and CM were measured and the sum, defined as the posterior fossa fluid (PFF) area was calculated. Reference ranges were constructed in relation to the crown-rump length. The study group consisted of 21 fetuses with open spina bifida and showed in all cases a single pocket of fluid in the posterior fossa. Fetuses with no fluid in the fossa were excluded. This PFF-area was measured and compared with the reference range of the IT-area and the PFF-area of normal fetuses and Z-scores were calculated. Results: In normal fetuses, a significant increase of the IT-, the CM- and the PFF-area was found as a sign of the expanding posterior fossa. The mean PFF-area increased from 8.55 to 29.72 mm2 in the observation period. Fetuses with open spina bifida had reduced fluid in the posterior fossa with values ranging between 2.39 and 5.08 mm2 and significantly lower Z-scores. Conclusions: Fetuses with open spina bifida have an abnormally small posterior fossa at 11-13 weeks' and in cases where the cerebrospinal fluid is still present, the fluid area in the midsagittal plane is reduced when compared to normal fetuses. Area fluid assessment can be an additional useful measurement in suspicious cases for open spina bifida in early gestation.