Differential diagnosis
DWM has a large number of conditions that can present highly similarly on imaging and confound diagnosis. Blakes pouch cyst
Blakes pouch cyst (BPC), or persistent Blakes pouch, is a condition that arises when Blakes pouch, an invagination in the fourth ventricle that ruptures at around 4 months of gestation to form the foramen of Magendie (medial aperture), fails to rupture. This can lead to a dilated fourth ventricle and subsequent hydrocephalus of all four ventricles.In a Blakes pouch cyst, unlike in DWM:
The cerebellum is not hypoplastic, though it may be compressed by the enlarged posterior fossa (mass effect). The posterior fossa is not enlarged. The cerebellar tentorium/confluence of sinuses is not raised. Hydrocephalus, when it occurs, involves all four ventricles.Some authors, however, consider Blakes pouch cyst part of a continuum with DWM (the "Dandy–Walker continuum"). Mega cisterna magna
Mega cisterna magna is a condition in which the cisterna magna, the subarachnoid cistern below the fourth ventricle, is enlarged. It has been proposed to be due to a delayed rupture of Blakes pouch rather than a failed rupture.In mega cisterna magna, unlike in DWM:
The cerebellum is not usually hypoplastic. The fourth ventricle is of relatively normal shape. Hydrocephalus is uncommon.There is debate as to whether this malformation is distinct from DWM or forms part of the "Dandy–Walker continuum". Posterior fossa arachnoid cyst
An arachnoid cyst is a collection of cerebrospinal fluid (CSF) in the arachnoid mater.
propensity, to develop spontaneous bleeding episodes and excessive bleeding after even minor tissue injuries and surgeries; however, individuals with any of these disorders may also exhibit a propensity to pathological thrombosis episodes.Treatment of these disorders generally involves specialized centers and the establishment of preventive measures designed based on each individuals personal and family histories of the frequency and severity of previous bleeding and thrombosis episodes, and, in a select few cases, the predicted propensity of the genetic mutations which underlie their disorders to cause bleeding and thrombosis. Signs and symptoms
Afibrinogenemia is typically the most severe of the three disorders. Common symptoms include bleeding of the umbilical cord at birth, traumatic and surgical bleeding, GI tract, oral and mucosal bleeding, spontaneous splenic rupture, and rarely intracranial hemorrhage and articular bleeding. Symptoms of hypofibrinogenemia varies from mild to severe, but can include bleeding of the GI tract, oral and mucosal bleeding, and very rarely intracranial bleeding. More commonly it presents during traumatic bleeding or surgical procedures. Most cases (60%) of dysfibrinogenemia are asymptomatic, but 28% exhibit hemorrhaging similar to that described above while 20% exhibit thrombosis (i.e. excessive clotting). Causes
The disorders associated with Factor I deficiency are generally inherited, although certain liver diseases can also affect fibrinogen levels and function (e.g. cirrhosis). Afibrinogenemia is a recessive inherited disorder, where both parents must be carriers. Hypofibrinogenemia and dysfibrinogenemia can be dominant (i.e. only one parent needs to be a carrier) or recessive. The origin of the disorders is traced back to three possible genes: FGA, FGB, or FGG.