33 - Cadaveric Dissection of Hyperostosis Frontalis Interna: A Case Report

Poster Board Number: 33
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Abstract Body : Introduction / Objective: Often seen as a benign secondary diagnostic finding, hyperostosis frontalis interna (HFI) is typified by the accretion of bone on the inside of the frontal bone and has been reported in varying frequency among post-menopausal females ranging between 5 and 18%. A presence of HFI is dependent upon both frontal bone thickness and noted waviness of the frontal bone internal plate. In reported cases, the top most part of the skull or calvaria has extensive, bilateral frontal bone thickening with an irregular contour in the form of nodules. The etiology and specific clinical manifestations are yet unknown; however a contemporary hypothesis focuses on hormonal stimulation. The purpose of this case report is to describe the findings of a routine dissection of a 90-year-old female cadaver with a history of vascular dementia revealing a novel case of hyperostosis frontalis interna.

Materials / Methods: Research methodology is a case report of a typical cadaveric dissection of a 90 year old female with a history of vascular dementia. Minimal medical history was available. No histological studies or computed tomography (CT) were available. The cranial skin was dissected from the outer skull, and the calvaria and brain were removed.

Results: Thickening of the frontal bone’s inside surface with asymmetrical nodular growths was observed. Noted thickening of the skull cap was present circumferentially with an unusual amount of difficulty in removal. Removal of the brain revealed bilateral frontal lobe compression. Anteriorly, the dura was fixed to the skull and the falx cerebri appeared to be non-existent. On visual inspection it appeared that the nodular growths infiltrated the dura. The posterior brain appeared more typical in nature while the anterior brain appeared less dense. The skull had a novel contour posteriorly with a noted concavity between the parietal bones.

Conclusion: This case presents the observed findings of HFI during a routine dissection of a 90 year old female with a known history of dementia. Noted frontal bone thickening, asymmetrical nodular protrusions from the inner surface, adhered dura, degraded falx cerebri, patient age, and deformed frontal lobes contribute to the case presentation.

Significance / Implication: The presence of HFI suggests a reduction in potential brain volume that may have clinical significance indicating the onset or existence of a degenerative brain process. Closely attached dura and cerebrum compression in cases of HFI has been previously reported. This observed case of HFI revealed a degradation of the falx cerebri contrary to previous reports of frontal bone midline sparing. It is unclear that the findings were directly related to the death of the patient however medical reports link dementia of vascular origin. With no reported history of head trauma, the posterior concave skull depression may be related to a deformity of the posterior fontanelle. This case presentation may represent one of the more unique and severe forms of HFI: Class C. For this case presentation it is plausible that the HFI disease process may have contributed, in part, to the medically reported dementia symptoms in this patient. By disseminating this report of a unique manifestation of HFI, it is intended to help clinicians when evaluating patients with this condition. Further research is needed linking the presence of frontal bone inner plate defects with pathological brain symptoms such as dementia.

Funding Sources: All funding is internal.