The parietal notch (Brammer's pointer): Accuracy of a surface landmark for temporal bone surgery

Area of Science:

• Anatomy
• Surgical Anatomy
• Neurosurgery

Background:

• No reliable surface landmark currently approximates the anterior border of the sigmoid sinus.
• The temporal line's accuracy in identifying the tegmen near the sinodural angle is questionable.

Purpose of the Study:

• To examine the reliability of the parietal notch as a surface landmark for the sigmoid sinus at the sinodural angle.

Main Methods:

• Forty-seven cadaveric temporal bones were analyzed.
• The parietal notch and sinodural angle were identified, marked, and CT imaged.
• Distances between landmarks were measured using PACS software.

Main Results:

• The parietal notch was identified in 43/47 specimens.
• It was located posterior (90.6%) and superior (65%) to the sinodural angle.
• The average horizontal distance was 6.1 mm, and vertical distance was 0.8 mm.

Conclusions:

• The parietal notch is identifiable in most temporal bones.
• It approximates the anterior sigmoid sinus border and tegmen level.
• It aids in defining mastoid dissection margins and assists surgeons.