Relationship between pharyngitis and peri‐odontoid pannus: A new etiology for someChiariImalformations?

Abstract

The pathophysiology underlying Chiari I malformations (CIMs) provides room for debate with several theories attempting to address this issue. We retrospectively reviewed many of our past patients with pediatric CIMs (specifically, those with peri-odontoid pannus), and present a hypothesis for the development of the malformation in some of said patients. Our experience with the pediatric CIM has shown that almost 1 in 20 patients who present with symptoms is found to have a peri-odontoid pannus. These masses ranged in size from 4 to 11 mm in diameter. Forty percent had a history of clinically significant pharyngitis or pharyngeal abscess. Pannus formation around the dens (odontoid) resulted in ventral compression of the craniocervical junction in each of these patients. Highlighting the hypermobility that causes such lesions, following fusion, the pannus and symptoms in several patients were diminished. Impairment of normal cerebrospinal fluid circulation out of the fourth ventricle and across the craniocervical junction appears to be a plausible endpoint in this discussion and a suitable explanation for some patients with CIM. Still, the mechanisms by which cerebrospinal fluid circulation is compromised may be variable and are not well understood. This is the first study dedicated to the evaluation of pannus formation in the CIM population. We hypothesize that pharyngeal inflammatory conditions contribute to the formation and progression of hindbrain herniation in a small subset of patients with CIMs.

The odontoid process: a comprehensive review of its anatomy, embryology, and variations

“…8) and other skeletal disorders affecting the CVJ [14,21]. This posterior deviation of the odontoid process has been speculated to arise from peri-odontoid inflammatory processes that remodel the apical part of this process [22].…”

Chiari I Malformation and Spinal Cord Ischemia in a Cadaver

“…There are many theories concerning the pathophysiology of CIM. Chiari attributed CIM to hydrocephalus, although we now know that less than 10% of CIM patients present with hydrocephalus [ 2 - 3 ]. Another theory has focused on mismatched rates of bone and brain development.…”

“…Theoretically, a small posterior cranial fossa would limit proper brain development and might result in hindbrain herniation through the foramen magnum. Animal models with underdeveloped posterior cranial fossae support this theory [ 2 ]. The spinal cord tethering theory states that tension forces herniation of the hindbrain; however, this does not successfully explain other presentations of CIM [ 4 ].…”

“…The hydrodynamic theory is based on the craniospinal pressure gradient and dictates that pulsatile pressure from the supratentorial region causes cerebellar herniation and cerebrospinal fluid flow reversal, resulting in syringomyelia. The hydrodynamic theory does not properly explain acquired CIM (i.e., after multiple lumbar punctures) [ 2 - 3 ]. Stenosis of the subarachnoid space adjacent to the foramen magnum can cause CIM due to impaired cerebrospinal fluid flow [ 5 ].…”

Sagittal MRI often overestimates the degree of cerebellar tonsillar ectopia: a potential for misdiagnosis of the Chiari I malformation

“…The current diagnosis of Chiari I malformation (CIM) depends mainly on the presence of herniated cerebellar tonsils on MR images and almost exclusively on midline sagittal slices. What constitutes cerebellar tonsillar herniation versus cerebellar tonsillar ectopia is a question that has had varied answers by different authors [2][3][4][5]. With the advent of MRI, it became necessary to formulate criteria that standardize the identification of CIM using MR imaging [2].…”