The anterior fontanelle (bregmatic fontanelle, frontal fontanelle) is the largest
fontanelle
A fontanelle (or fontanel) (colloquially, soft spot) is an anatomical feature of the infant human skull comprising soft membranous gaps ( sutures) between the cranial bones that make up the calvaria of a fetus or an infant. Fontanelles allow ...
, and is placed at the junction of the
sagittal suture,
coronal suture
The coronal suture is a dense, fibrous connective tissue joint that separates the two parietal bones from the frontal bone of the skull.
Structure
The coronal suture lies between the paired parietal bones and the frontal bone of the skull ...
, and
frontal suture
The frontal suture is a fibrous joint that divides the two halves of the frontal bone of the skull in infants and children. Typically, it completely fuses between three and nine months of age, with the two halves of the frontal bone being fused t ...
; it is
lozenge
Lozenge or losange may refer to:
*Lozenge (shape), a type of rhombus
*Throat lozenge, a tablet intended to be dissolved slowly in the mouth to suppress throat ailments
*Lozenge (heraldry), a diamond-shaped object that can be placed on the field of ...
-shaped, and measures about 4 cm in its antero-posterior and 2.5 cm in its transverse diameter. The fontanelle allows the skull to deform during birth to ease its passage through the birth canal and for expansion of the brain after birth.
The anterior fontanelle typically closes between the ages of 12 and 18 months.
Clinical significance
The anterior fontanelle is useful clinically. Examination of an infant includes palpating the anterior fontanelle. A sunken fontanelle indicates
dehydration
In physiology, dehydration is a lack of total body water, with an accompanying disruption of metabolic processes. It occurs when free water loss exceeds free water intake, usually due to exercise, disease, or high environmental temperature. Mil ...
whereas a very tense or bulging anterior fontanelle indicates raised
intracranial pressure
Intracranial pressure (ICP) is the pressure exerted by fluids such as cerebrospinal fluid (CSF) inside the skull and on the brain tissue. ICP is measured in millimeters of mercury ( mmHg) and at rest, is normally 7–15 mmHg for a supine adul ...
. However, this is not a certain indicator for raised pressure as prolonged crying by the baby may produce the same effect. A full anterior fontanelle may also be indicative of
neonatal meningitis, specifically acute bacterial meningitis.
Additional images
File:Slide1MIA.JPG, Skull of newborn. Anterior view.
See also
*
Bregma
External links
*
{{Authority control
Skull