Brooke's Flashcards
What is hyperdense on CT?
Hyperdense=bright on CT
Blood and calcifications
What is hypodense on CT?
Hypodense=dark on CT compared to surrounding brain.
Could be infarction, edema, pneumocephalus.
Pneumonic for an emergent CT head.
Blood Can Be Very Bad
- Blood - look for epidural/subdural hematomas, ICH, IVH, subarachnoid hemorrhage and (also) extracranial hemorrhage.
- Cisterns - look for the presence of blood, effacement and asymmetry in four key cisterns (perimesencephalic, suprasellar, quadrigeminal and Sylvian cisterns).
- Brain - look for asymmetry or effacement of the sulcal pattern, gray-white matter differentiation, structural shifts and abnormal hypodensities (e.g. air, edema, fat) or hyperdensities (e.g. blood, calcification).
- Ventricles - look for intraventricular hemorrhage, ventricular effacement or shift and for hydrocephalus.
- Bone - look for skull fractures (especially basal) on bone windows (soft tissue swelling, mastoid air cells and paranasal sinuses fluid in the setting of trauma should raise the possibility of a skull fracture; intracranial air means that the skull and the dura have been violated somewhere).
Things that are bright on FLAIR imaging?
- Acute SAH.
- Edema.
- Acute infarcts.
There are others but those are the big ones.
When does the anterior fontanelle normally close?
- 4-26 months of age.
When does the posterior fontanelle normally close?
- Before 2 months of age.
An enlarged posterior fontanelle can occur in what conditions?
- Congenital hypothyroidism.
- Trisomy syndromes.
- Rickets.
- Osteogenesis imperfecta.
- Hydrocephalus.
A depressed anterior fontanelle can be a sign of what condition?
- Dehydration.
When does the embryonic skull begin to form?
- Between the 23rd and 26th day of gestation.
What is thought to initiate cranial suture formation?
- Osteogenic fronts, which consist of osteoprogenitor cells and osteoblasts at the leading edges of developing bone.
What factors determine normal suture formation?
- Bone deposition by osteoblasts.
- Bone remodeling by osteoclasts.
- Apoptosis in the frontal boundaries.
- Local interactions between dura mata and the sutures.
- Growth factors (fibroblast growth factor receptor and transforming growth factor).
True or false: The primary influence for cranial growth is the growing brain.
True.
Name the sutures of the cranium.
- Metopic (between both frontal bones).
- Sagittal (between both parietal bones).
- Two coronal (between parietal and frontal bones).
- Two lambdoid (between occipital and parietal bones).
- Squamosal (between parietal, temporal, and sphenoid bones).
Which of the sutures naturally closes earliest?
- Metopic suture - usually closed by 9 months of age.
What are the 4 principles associated with suture closing?
- Calvarial bones directly next to the fused suture act as a single bone plate with decreased growth potential.
- Asymmetrical bone deposition occurs at the sutures along the perimeter of the bone plate with increased bone deposition at the outer margin.
- Nonperimeter sutures in line with the fused suture deposit bone symmetrically at their suture edges.
- Perimeter sutures adjacent to the fused suture compensate to a greater degree than the other distant sutures.
What clinically similar condition must be differentiated from true craniosynostosis?
- Deformational plagiocephaly, which is more common than craniosynostosis and results from external forces causing skull deformation into a parallelogram shape.
What types of craniosynostosis resemble deformational plagiocephaly?
- Unilateral coronal and lambdoid craniosynostosis.
What is scaphocephaly?
- Craniosynostosis caused by sagittal suture closure.
What is frontal plagiocephaly?
- Craniosynostosis caused by unilateral coronal suture closure.
What is trigonocephaly?
- Craniosynostosis caused by metopic suture closure.
What is posterior plagiocephaly?
- Craniosynostosis caused by unilateral lambdoid closure.
What is brachycephaly?
- Craniosynostosis caused by bilateral lambdoid suture closures.
True or false: Sagittal craniosynostosis is the most common form.
- True - accounts for 40-60% of all craniosynostosis cases.
How does the head look in sagittal synostosis?
- AP elongation with frontal and/or occipital bossing and biparietal and bitemporal narrowing (long, skinny head).
How does the head look in unilateral coronal synostosis?
- Flattened ipsilateral forehead and parietal area, compensatory contralateral frontal bossing and ipsilateral temporal bulging.
- Nasal root deviation to ipsilateral side.
- Anterior displacement of ipsilateral ear.
- Superiorly displaced sphenoid wing –> heightened orbit (Harlequin eye).
How does the head look in bilateral coronal synostosis?
- Flattened occiput and forehead, anterior displacement of the skull vertex, widening of the upper face, prominent globes from decreased AP diameter (basically a short, wide head).
How does the head look in metopic synostosis?
- Trigonocephaly - fonrtal keel, narrowed bitemporal width, anterior displacement of coronal suture, retrusion of orbital rims, reduced frontonasal angle.
True or false: Lambdoid synostosis is the rarest of the nonsyndromic craniosynostoses?
- True - lambdoid synostosis accounts for 2-3%.
How does the head look in lambdoid synostosis?
- Unilateral occipitoparietal flattening.
- Contralateral posterior bossing.
- Prominent occipitomastoid bulge.
- Posterior and inferior displacement of ear.
- Trapezoid shape when seen from above.
Craniosynostosis patients are at risk for increased ICPs. What is the mechanism?
- Distorted subarachnoid spaces lead to changes in CSF circulation.
What are arachnoid cysts composed of?
- CSF-like fluid surrounded by an arachnoidal membranous wall.
Why do arachnoid cysts form?
- Abnormal CSF flow during development causes cyst formation.
Where are arachnoid cysts most commonly located?
- Sylvian fissure and middle fossa.
What are other locations of arachnoid cysts other than the Sylvian fissure?
- Cerebellopontine angle.
- Quadrigeminal cistern.
- Sellar and suprasellar areas.
True or false: arachnoid cysts have high malignant potential?
- False, most are asymptomatic and benign.
What are the main surgical options for treatment of arachnoid cysts?
- Cyst shunting.
- Open fenestration.
- Endoscopic fenestration.
Most won’t need any type of surgical intervention!
