Recurrent Meningitis from an Uncommon Midline Conduit
Year: 2025
Type: article
Study design: Case Report
Abstract: Sir, Recurrent bacterial meningitis, a potentially life-threatening condition, may be predisposed to by structural aberrations in up to two-thirds of the cases.[1] The most frequent route of infection is through the skull base. Posttraumatic CSF fistula is one of the most common causes and is responsible for approximately 28% of cases. Less frequently, a pre-existent conduit might transmit the nasopharyngeal pathogenic flora into the meningeal compartment. We present one such entity in a patient who was referred for evaluation of recurrent meningitis and sensorineural hearing loss. A 29-year-old man was referred for further evaluation for the cause of recurrent meningitis. His last episode was two months earlier, when he was admitted with complaints of fever, headache, vomiting, and drowsiness. With a clinical diagnosis of recurrent meningitis, CSF examination revealed elevated white blood cell counts (predominantly polymorphs), elevated protein, and decreased glucose. He was managed on intravenous antibiotics, and he recovered during his in-hospital course. On elaboration of the history of illness, his first episode of meningitis was at the age of 12 years when he suffered similar complaints of fever, headache, vomiting, and altered sensorium that was followed by hearing loss. CSF examination during that episode disclosed similar microscopic and biochemical findings. He had documented history of multiple episodes of meningitis. He had no other concomitant ailment suggestive of remote infective foci. No history of ear discharge, head trauma, CSF rhinorrhea, nasal discharge, and developmental delay was documented. No tell-tale evidence of spinal dysraphism was evident. No history of skull base surgery or trauma was reported. The tailored algorithm for the patient began with imaging. Helical CECT revealed [Figure 1] a circumscribed, tubular corticated bony defect of approximately 8 mm diameter extending between the nasopharyngeal roof and the floor of widened sella. Formulating a diagnosis of a persistent craniopharyngeal duct, an MRI [Figures 2-6] was performed. It revealed CSF isointense signal traversing the defect and extending up to the nasopharynx. Three-dimensional Constructive Interference in steady state (CISS3d) sequences with heavy T2 weighting demonstrated the continuity of a markedly enlarged infundibular recess of the third ventricle across the defect extending up to the nasopharyngeal roof. No demonstrable cyst wall was noted. The contents were isointense to CSF with turbulence related artefacts highlighting the continuity with the ventricular system. The anterior aspect of the stretched infundibulum showed differential T1 hyperintense signal, raising the suspicion of neurohypophyseal/posterior pituitary ectopia due to a stalk interruption. The inferior aspect of the herniated infundibular recess was in continuity with a differential signal intensity structure that demonstrated intense post contrast enhancement, morphologically resembling an ectopic/herniated adenohypophysis. There was no abnormal leptomeningeal enhancement. Intracranial or facial midline malformations were absent.Figure 1: Axial (a) sagittal (b) coronal (c) CT reconstructions reveal the midline, circumscribed, corticated defect in the sphenoid body in the floor of the widened sellaFigure 2: Axial T1-weighted sections at the level of the widened sella show CSF isointense signal of the infundibulum and T1 hyperintense signal draped at the anterior aspect of this structure, raising the possibility for neurohypophyseal ectopia as a consequence of pituitary stalk interruptionFigure 3: Coronal T2-weighted fat-suppressed image discloses a widened sella with the midline defect in the floor and contiguity of CSF isointense signal across the defect with a dysmorphic soft tissue, the adenohypophyseal equivalent suspended at the inferior aspect of the CSF signal in the region of the nasopharyngeal roofFigure 4: Coronal T2-weighted fat suppressed image discloses a widened sella with the midline defect in the floor and contiguity of CSF isointense signal across the defect with a dysmorphic soft tissue, the adenohypophyseal equivalent suspended at the inferior aspect of the CSF signal in the region of the nasopharyngeal roofFigure 5: Sagittal CISS-3D shows the ballooned infundibular recess occupying the widened sella and the T2-hyperintense soft tissue in the roof of the nasopharynx. The presellar T2-hyperintense content represents mucusFigure 6: Sagittal T1-weighted postcontrast images reveal enhancement of the ectopic pituitaryThe endocrine evaluation documented no pituitary dysfunction. The audiological evaluation revealed bilateral sensorineural hearing loss. The evaluation for immunodeficiency returned negative. The patient was initiated on antibiotic prophylaxis and the 6 months follow-up had no evidence of recurrence of the symptoms. No surgical intervention was performed. Congenital malformations rendering an individual prone to recurrent meningitis include meningocele/meningomyelocele, skull base defects, inner ear anomalies, dermal sinus tract, neurenteric cyst. However, the most common anatomical cause of recurrent meningitis, is CSF leak post-trauma.[1,2] With the background of trauma to the skull base, delayed CSF leaks after 3 months have been reported in up to 5% of cases, while presentation beyond one year is rare.[2] Craniopharyngeal canal is an uncommon, midline, corticated deficiency with ontogenic underpinnings. The current consensus favors it as an aberration in the closure of the Rathke’s pouch, the adenohypophyseal anlage.[3,4] The pituitary development is conceived as originating from adherence of the stomodeum (adenohypophyseal primordium) and diencephalic floor (neurohypophyseal primordium).[5] The orchestrated ontogenic evolution progresses through the formation of an adenohypophyseal pouch, suspended by a stalk, which is later obliterated by the post sphenoid cartilage.[6-8] Aberrations in the postsphenoid cartilage fusion is the proposed mechanism for the formation of the craniopharyngeal canal.[9] The craniopharyngeal canal, as an incidental finding has been reported in approximately 0.42% of the population. The earliest description dates to 1904 by Sokolow et al.,[10] the later imaging-replete accounts largely being restricted to case reports.[11] Variations existed in the quantitative and qualitative descriptors of these lesions until a recent comprehensive classification by Abele et al.[9] This classification divides craniopharyngeal canal into three types, primarily based on dimensions of the defect. Type 1–3 have dimensions of approximately 0.7–1.1 mm, 3.5–4.4 mm, and 5.9–31.0 mm, respectively, and Type 3 is further divided into subtypes A–C based on the presence of cephalocele, tumor, or both, respectively. Such a system guides surgical planning and is useful further evaluation of pituitary dysfunction. The index case with the adenohypophyseal ectopia, dimensions, and absence of tumor would be appropriately classified as Type 3A. The spectrum of clinical manifestation of CPC is diverse. Small sized defects may be an incidental finding on imaging. The range of clinical presentations may span nasopharyngeal mass causing obstruction, CSF rhinorrhea, recurrent meningitis, and pituitary dysfunction.[12] Less frequent manifestations include seizures, diminution of vision, and PHACE (posterior fossa malformations, hemangiomas, arterial abnormalities, cardiac defects, and eye abnormalities) syndrome. Co-existent midline anomalies like facial clefts, cleft lip, cleft palate, and aberrations in adenohypophyseal organization are described. In young children with large nasopharyngeal encephaloceles, an extended endonasal approach may be adopted for surgical repair and reconstruction of the skull base. It helps achieve early postoperative recovery and avoids morbid alternative transfacial approaches.[12,13] Opinion varies on the alternative types and access for surgical management, the options being transcranial, transpalatal, and transoral approaches. Correct diagnosis of this embryological phenomenon can possibly obviate (iatrogenic) pituitary dysfunction, CSF leak, and inappropriate surgery. To conclude, a careful inspection of the skull base is warranted in the evaluation of recurrent meningitis. A congenital anatomic predilection as in the case of craniopharyngeal canal ought to be borne in mind in such instances. The knowledge of the scheme of the embryological development of the hypophysis would help further understand this rare entity. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
Source: Neurology India
Authors: Karthik Kulanthaivelu, Chandrajit Prasad
Language: English
Subfield: Microbiology
Field: Immunology and Microbiology
Domain: Life Sciences
Open Access status: hybrid
OpenAlex ID: W4407798748