Skull Shape Variations

Variations in Skull Shape

• Skull shape variations include craniosynostoses, positional skull deformities, anencephaly, microcephaly, platybasia, and cranial suture diastasis.

Abnormal Head Shape

• Premature suture closure in newborns leads to craniosynostosis.
• Continuous external force can cause positional (deformational) skull deformities.
• Positional skull deformities can result from intrauterine factors, birth canal effects, or positioning in the first 4-12 weeks of life.

Craniosynostosis

• Most cases are due to an intrinsic sutural defect, termed primary craniosynostosis.
• Craniosynostosis results in restricted growth perpendicular to the affected suture and exaggerated growth parallel to it.

Monosutural Craniosynostosis Types

• Scaphocephaly involves the sagittal suture.
• Brachycephaly involves bi-coronal and/or bi-lambdoidal sutures.
• Trigonocephaly involves the metopic (frontal) suture.
• Plagiocephaly (anterior) involves the unilateral coronal suture.
• Plagiocephaly (posterior) involves the unilateral lambdoidal suture.

Multisutural Craniosynostosis Types

• Turricephaly involves the coronal suture plus any other suture.
• Pansynostosis involves three or more sutures.
• Microcephaly involves all sutures.
• Syndromes can cause Craniosynostosis along with cardiac, kidney, or skeletal anomalies.

Scaphocephaly

• The most common form (40%) of monosutural craniosynostosis.
• It involves premature closure of the sagittal suture.
• Results in an elongated head in the A-P direction and a narrowed biparietal width in the LAT direction.
• A prominent midline sagittal ridge is palpable superficially.
• Some infants may have an associated "saddle" deformity at the vertex, resulting in a peanut-shaped head.
• Male predominance
• Radiographic appearance: AP is a narrow bullet-shaped head and lateral is an elongated head.

Synostotic Anterior Plagiocephaly

• Also known as frontal plagiocephaly, it's the second most common type of monosutural craniosynostosis.
• Results from premature closure of one coronal suture.
• Forehead flattens on the affected side, resulting in the eye socket being drawn up "harlequin eye", and the nose may deviate.
• Heads are "slanting".

Brachycephaly

• A less common form of monosutural craniosynostosis.
• Frontal skull base is small with shallow eye sockets and the head is shortened in A-P direction and broad in LAT direction.
• Premature closure of BOTH coronal sutures, referred to as BI-CORONAL SYNOSTOSIS.
• Heads are "short".

Trigonocephaly

• Rare form of monosutural craniosynostosis.
• Premature closure of the metopic (frontal) suture.
• Associated with a small frontal head volume, pointy forehead, and orbital hypotelorism.
• Narrow in front and broad in the back.
• Palpable midline metopic ridge anteriorly.

Synostotic Posterior Plagiocephaly

• A rare type (2%) of monosutural craniosynostosis, also known as occipital plagiocephaly.
• Results from a premature closure of one lambdoidal suture.
• Posterior skull flattens on the affected side, along with compensatory growth of the mastoid process and unique "tilt" in the cranial base.
• Associated with Chiari malformation.

Turricephaly

• A type of multisutural craniosynostosis which involves premature closure of coronal plus any other suture.
• Head appears tall with reduced length and width, also known as "high head syndrome"
• Includes Oxicephaly (Acrocephaly) which is its most severe form and includes fused sagittal, coronal and lambdoid sutures (tower- like skull)

Bathrocephaly

• Normal variation in skull shape as an outward convex bulge of the mid-portion of the occipital bone.
• Associated with persistent mendosal suture (accessory occipital suture)
• Usually found bilaterally.

Positional Plagiocephaly

• Asymmetrical flattening of one side of the skull with open sutures.
• Back of head flattened on one side with ear misalignment and forward shift on the flat side.
• Can cause Torticollis which causes a skew head.
• Most common type of infant flat head syndrome.

Positional Brachycephaly

• Is the second-most common type of flat head syndrome.
• A symmetrically flat (evenly) head in the back, that is wide from side to side, and with occasional forehead bulges.
• Encourage tummy time because spending a lot of time on their back causes the issue.

Positional Dolichocephaly

• Also known as deformational dolichocephaly.
• Typically occurs in preterm infants.
• Characterized by an Elongated head without associated parietal narrowing.
• No midline sagittal ridge.
• May result from a breech birth.

Anencephaly

• Congenital anomaly of brain development diagnosed by week 16-20 of pregnancy with US.
• Classic form called MEROANENCEPHALY.
• Lack of cranial vault bones and exposed neural tissue from defective neural tube closure.
• Folic Acid supplements prevents it during pregnancy.

Microcephaly

• Smaller cranial vault than normal leading to a small head and high ICP.
• intellectual disability, poor motor skills, speech issues, abnormal facial features, vision issues, hearing loss, seizures & and dwarfism accompanies.
• The genetic syndromes Down and Zika virus often accompany.
• Sutures prematurely fuse due to Primary Craniosynostosis,

Platybasia

• Abnormal flattening of the base of the skull which causes secondary neurological abnormalities and hydrocephalus from a compressed brainstem.
• Malformation occurring between the occipital bone and the cervical spine (craniocervical junction=
• Basilar & condylar portions of occipital bone displaced upward by cervical spine cause Basilar invagination (Impression) impingement on brainstem
• Associated with both osteomalacia and osteogenesis imperfecta as secondary conditions.

Cranial Suture Diastasis

• Abnormal widening or separation of cranial sutures.
• Causes can be increased Intracranial Pressure (ICP) or may be associated with fractures and tumors.
• Caused by fractures.
• Plain radiographic images show it.

Physiologic Intracranial Calcifications

• Calcifications of the pineal gland, falx cerebri, choroid plexus, habenular commissure, and sella turcica.

Pineal Gland

• Small, midline pea-shaped endocrine gland located deep in the brains center.
• Melatonin gets released cyclically at night.
• Calcification occurs at different degrees,
• Normal is 3 to 5mm.
• An intracranial pathology is indicated by displacement of more than 3mm, indicating an intracranial pathology

Calcified Pineal Gland

• Best seen by meticulous positioning, AP or PA midline and superior portions of temporal bones.

Falx Cerebri

• Projects into dividing cerebral hemispheres and is an inner fold of dural matter found on mid-sagittal plane.
• Extends from cranial valult margins to crista Galli of ethmoid bone along inner aspect.

Calcified Falx Cerebri

• A thin , dense line on AP or PA images is seen when calcified (normally occurs in elderly).

Glomera of Choroid Plexus

• Most common intracranial calcification with a 75% incidence rate at age 50.
• Effects the of vascular network of lateral ventricles.
• Radiographic appearance is either a few small dots or more than 1cm in diameter.
• located 2 ½ to 3cm away from midline, and superior/lateral to the pineal gland on AP or 5cm S/P to pineal gland on LAT

Habenular Commissure

• White matter fibre bundles that bridges midline structure and connects opposite hemispheres of the brain.
• Functions to ensure integration between left and right brain structures.
• Superior and anterior of gland and posterior to ventricle.
• Located on the lateral.

Sella Turcica Calcifications

• Can indicate calcified pituitary adenomas and craniopharyngiomas.

Normal Cranial Radiolucencies

• Include fractures, sutures, and vascular markings.

Fractures

• Translucent lines with // margins with no tapering.
• Sharply demarcated and more radiolucent.
• Effects both tables.

Sutures

• Winding, serpiginous lines and symmetrical.
• Fine sclerotic or corticated margins at typical anatomical structures.

Vascular Markings

• Meningeal tapers as the run down peripherally.
• Has branching pattern and symmetrical.

Arachnoid Granulations (Villi)

• Invaginated tufts of dural venous sinuses of arachnoid layer that allows CSF to enter the bloodstream.
• Contains parasagittal superior santal sinus.
• Small, and bone irregular defect for around 2 -8mm in size
• The bodies reserve the term.

Arterial Grooves

• Prominent Middle meningeal artier on inner table of skull travels along foramina and travels up laterally.

Venous Plexuses Within Diploë

• Located on valveless channels located inside and outside layers located within calvaria skull.
• Connection that's important between layers on veins

Venous Lakes

• Enlarged dual venous spaces of skull on parasagittal region.
• Located among vascular walls.

Cranial Sutures

• Radiolucent, a zigzagging feature on adults with squamasol x2 and cornical.
• Between halves lies bone where neonates may fuse by 2.

Mastoid Air Cells

• Are part aerated bone found on temporal bone.
• Speckled on infro-lateral skull located superiorly on mastoid tips.

Trauma

• Involves skull fractures.

Linear Skull Fractures

• Traverse full thickness breaks that come outer to inner parts where bones don't get displayed.

Diastatic Skull Fractures

• Line touches one or more cranial sutures in the skull and are seen among young children and infants.

Depressed Skull Fractures

• Bone bits are displaced and surgery may be needed from overlaying pushing.
• Compounded and overlying skin are lacerated through parnasal.

Comminuted Skull Fractures

• Division from linear lines where fragments can penetrate which may cause hemorrhage's .

Skull Fractures

• Can be viewed through x-ray.

Basilar Fractures

• Linear fractures of bones may cause racoon eyes, and battles sign causing bruising.
• May cause blood on sinuses also.
• Spinal consult needed for open communications.

Other Traumatic Skull Fractures

• Projectile objects including bullets cause cause trauma which shatter.
• Two year olds can be victims from objects penetrated.