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Radiology of ventricles


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Published in: Health & Medicine

Radiology of ventricles

  2. 2. Anatomic overview. • The brain CSF spaces- ventricular system and subarachnoid spaces (SAS). • The ventricular system -4 interconnected CSF-filled, ependymal-lined cavities that lie deep within the brain. • The paired lateral ventricles communicate with the 3rd ventricle via the Y-shaped foramen of Monro. • The 3rd ventricle communicates with the 4th ventricle via the cerebral aqueduct (of Sylvius). • In turn, the 4th ventricle communicates with the SAS via its outlet foramina (the midline foramen of Magendie and the 2 lateral foramina of Luschka).
  3. 3. Lateral ventricles. • Body, atrium, and 3 projections ("horns"). • The roof of the frontal horn is formed by the corpus callosum genu. • Laterally and inferiorly by the head of the caudate nucleus. • The septum pellucidum, a thin sheet of tissue that extends from the corpus callosum genu anteriorly to the foramen of Monro posteriorly, forms the medial borders of both frontal horns.
  4. 4. • The body of the lateral ventricle passes posteriorly under the corpus callosum. • Its floor is formed by the dorsal thalamus and its medial wall is bordered by the fornix. • Laterally, it curves around the body and tail of the caudate nucleus.
  5. 5. • The atrium contains the choroid plexus glomus and is formed by the confluence of the body with the temporal and occipital horns. • The temporal horn extends anteroinferiorly from the atrium and is bordered on its floor and medial wall by the hippocampus. • Its roof is formed by the tail of the caudate nucleus. • The occipital horn is surrounded entirely by white matter fiber tracts, principally the geniculocalcarine tract and the forceps major of the corpus callosum.
  6. 6. Lateral ventricle mass • Choroid plexus cysts (xanthogranulomas) are a common, generally age-related, degenerative finding with no clinical significance. • They are usually bilateral and calcified. • They may be hyperintense on FLAIR and occasionally show reduced diffusivity on DWI. • A strongly enhancing choroid plexus mass in a child is most likely a choroid plexus papilloma. • With the exception of the 4th ventricle, a choroid plexus mass in an adult is usually meningioma or metastasis, not a choroid plexus papilloma. • An innocent-appearing frontal horn mass in a middle-aged or older adult is most often a subependymoma. • A "bubbly" mass in the body of the lateral ventricle is usually a central neurocytoma. • Neurocysticercosis cysts can occur in all ages and in virtually every CSF space.
  7. 7. Foramen of Monro mass. • The most common "abnormality" here is a pseudolesion caused by CSF artifact. • Colloid cyst is the only relatively common pathology here. • It is rare in children and typically a lesion of adults. • Flow artifact can mimic a colloid cyst, but mass effect is absent. • In a child with an enhancing mass in the interventricular foramen, tuberous sclerosis with subependymal nodule &/or giant cell astrocytoma should be a consideration. • Masses such as ependymoma, papilloma, and metastasis are rare.
  8. 8. 3rd ventricle. • Single, slit-like, midline, vertically oriented cavity that lies between the thalami. • Roof- formed by the tela choroidea, a double layer of invaginated pia. • The lamina terminalis and anterior commissure lie along the anterior border of the 3rd ventricle. • Floor-formed by several critical anatomic structures. • From front to back these include the optic chiasm, hypothalamus with the tuber cinereum and infundibular stalk, mamillary bodies, and roof of the midbrain tegmentum.
  9. 9. • The 3rd ventricle has 2 inferiorly located CSF- filled projections, the slightly rounded optic recess and the more pointed infundibular recess. • Two small recesses, the suprapineal and pineal recesses, form the posterior border of the 3rd ventricle. • A variably sized interthalamic adhesion (also called the massa intermedia) lies between the lateral walls of the 3rd ventricle. • The massa intermedia is not a true commissure.
  10. 10. 3rd ventricle mass. • Most common "lesion" in this location is either CSF flow artifact or a normal structure (the massa intermedia). • Colloid cyst is the only common lesion that occurs in the 3rd ventricle; 99% are wedged into the foramen of Monro. • Extreme vertebrobasilar dolichoectasia can indent the 3rd ventricle, sometimes projecting upward as high as the interventricular foramen. • Primary neoplasms in children are uncommon here but include choroid plexus papilloma, germinoma, craniopharyngioma, and a sessile-type tuber cinereum hamartoma. • Primary neoplasms of the 3rd ventricle in adults are also uncommon, though an intraventricular macroadenoma and chordoid glioma are examples. • Neurocysticercosis occurs here but is uncommon.
  11. 11. 4th ventricle • Diamond-shaped cavity that lies between the pons anteriorly and the cerebellar vermis posteriorly. • Its roof is covered by the anterior (superior) medullary velum above and the inferior medullary velum below.
  12. 12. • The 4th ventricle has 5 distinctly shaped recesses. • The posterior superior recesses are paired, thin, flat CSF- filled pouches that cap the cerebellar tonsils. • The lateral recesses curve anterolaterally from the 4th ventricle, extending under the brachium pontis (major cerebellar peduncle) into the lower cerebellopontine angle cisterns. • The lateral recesses transmit choroid plexus through the foramina of Luschka into the adjacent subarachnoid spaces. • The fastigium is a triangular, blind-ending, dorsal midline outpouching that points towards the cerebellar vermis.
  13. 13. Cerebral aqueduct • Other than aqueductal stenosis, intrinsic lesions of the cerebral aqueduct are rare. • Most are related to masses in adjacent structures (e.g., tectal plate glioma).
  14. 14. 4th ventricle mass • Pediatric masses are the most common . • Medulloblastoma, ependymoma, and astrocytoma predominate. • Atypical teratoid-rhabdoid tumor (AT/RT) is a less common neoplasm that may occur here. It usually occurs in children under the age of 3 years and can mimic medulloblastoma. • Metastases to the choroid or ependyma are probably the most common 4th ventricle neoplasm of adults. • Primary neoplasms are rare. • Choroid plexus papilloma does occur . • Subependymoma is a lesion of middle-aged adults that is found in the inferior 4th ventricle, lying behind the pontomedullary junction. • A newly described rare neoplasm, rosette-forming glioneuronal tumor, is a midline mass of the 4th ventricle. It has no particular distinguishing imaging features and, although it may appear aggressive, it is a benign (WHO grade I) lesion. • Hemangioblastomas are intraaxial masses but may project into the 4th ventricle. • Epidermoid cysts and neurocysticercosis cysts can be found in all ages.
  16. 16. • Terminology • Focal reduction of cerebral aqueduct diameter • Imaging • Ventriculomegaly of lateral and 3rd ventricles with normal-sized 4th ventricle • ± periventricular interstitial edema (uncompensated hydrocephalus)
  17. 17. Differential Diagnoses • Obstructing extraventricular pathology – Neoplasm – Vein of Galen malformation – Quadrigeminal cistern arachnoid cyst • Obstructing intraventricular (aqueductal) pathology • Postinflammatory gliosis (aqueductal gliosis)
  18. 18. • Pathology • Congenital AS is common cause of fetal hydrocephalus • Aqueductal web and fork are pathological subsets • Clinical Issues • Onset often insidious, may occur at any time from birth to adulthood • DIAGNOSTIC CHECKLIST • Consider • Postinflammatory gliosis (aqueductal gliosis), particularly if history of prematurity or meningitis • Carefully scrutinize posterior 3rd ventricle, tectum, and tegmentum for neoplastic mass • Image Interpretation Pearls • Tectal astrocytomas large enough to obstruct aqueduct may be missed on routine CT scanning – MR more sensitive than CT for detecting obstructing mass lesion – Consider neurofibromatosis type 1 when tectal astrocytoma is identified
  20. 20. • Terminology • Ventriculomegaly with normal CSF pressure, altered CSF dynamics • Imaging • Ventricles/sylvian fissures symmetrically dilated – Out of proportion to sulcal enlargement – Hippocampus is normal (distinguishes from atrophy) • ± aqueductal flow void • Periventricular high signal transependymal CSF flow • 50-60% periventricular & deep white matter lesions • MRS: Lactate peaks in lateral ventricles in NPH • Aqueduct stroke volume > 42 μL reported to correlate with good response to shunt
  21. 21. • Differential Diagnoses • Normal aging brain • Alzheimer disease • Multi-infarct dementia (MID) • Subcortical arteriosclerotic encephalopathy
  22. 22. • Pathology • Leading theory: Poor venous compliance in superior sagittal sinus impairs CSF pulsations and CSF absorption through arachnoid granulations • Pathogenesis of NPH poorly understood • Clinical Issues • Heterogeneous syndrome (classic clinical triad = dementia, gait apraxia, urinary incontinence) • Image Interpretation Pearls • Intraventricular lactate level may be useful in differentiating NPH from other types of dementia
  23. 23. THANK U
  25. 25. • Terminology • Extraventricular obstructive hydrocephalus (EVOH) – "Communicating" hydrocephalus • Enlarged ventricles due to mismatch between CSF formation, absorption • Imaging • Obstruction distal to 4th ventricle outlet foramina • Size varies with duration of obstruction • All ventricles enlarged with no intraventricular obstructive cause • Lateral 3rd, 4th ventricles dilated • ± abnormal density/intensity of cisternal CSF ± leptomeningeal enhancement
  26. 26. • Top Differential Diagnoses • Intraventricular obstructive hydrocephalus • Ventricular enlargement 2° to parenchymal loss • Normal pressure hydrocephalus • Pathology • Subarachnoid hemorrhage – Most common cause of EVOH • Other etiologies include suppurative meningitis, neoplastic or inflammatory exudates • SAH, exudates may fibrose/occlude subarachnoid space • Clinical Issues • Headache, papilledema • Nausea, vomiting, diplopia (cranial nerve palsy) • Diagnostic Checklist • EVOH: Generalized ventricular enlargement with abnormal density/intensity in basal cisterns ± leptomeningeal enhancement
  28. 28. • Terminology • Intraventricular obstructive hydrocephalus (IVOH) = obstruction proximal to foramina of Luschka, Magendie – Acute (aIVOH) – Chronic "compensated" (cIVOH) • Imaging • aIVOH = "ballooned" ventricles plus indistinct ("blurred") margins – "Fingers" of CSF extend into periventricular WM – Most striking around ventricular horns (periventricular "halos") – After decompression, corpus callosum may show hyperintensity • cIVOH = "ballooned" ventricles without periventricular "halo"
  29. 29. • Top Differential Diagnoses • Ventricular enlargement 2° to parenchymal loss • Normal pressure hydrocephalus • Extraventricular obstructive hydrocephalus • Choroid plexus papilloma • Longstanding overt ventriculomegaly in adults • Pathology • Intraventricular obstruction to CSF flow – CSF production continues, ventricular pressure ↑ • CSF production continues, ventricular pressure ↑ • Ventricles expand, compress adjacent parenchyma • Periventricular interstitial fluid increases – Leads to myelin vacuolization, destruction • Leads to myelin vacuolization, destruction • Pathology varies depending on obstruction etiology • Diagnostic Checklist • Ventricle size generally correlates poorly with intracranial pressure • Image Interpretation Pearls • Size of ventricles generally correlates poorly with intracranial pressure • Pulsatile CSF may create confusing signal intensity, even mimic intraventricular mass • Ventricular asymmetry can be normal variant
  31. 31. • Imaging • Shunt failure → dilated ventricles + edema around ventricles, along catheter and reservoir • Use CT or MR to evaluate ventricle size, plain radiograph shunt series to identify mechanical shunt failure • Top Differential Diagnoses • Shunt failure with normal ventricle size or lack of interstitial edema • Noncompliant ("slit") ventricle syndrome • Acquired Chiari 1 malformation/tonsillar ectopia
  32. 32. • Pathology • Obstructive hydrocephalus: Secondary to physical blockage by tumor, adhesions, cyst • Communicating hydrocephalus: Secondary to ↓ CSF absorption across arachnoid granulations • Clinical Issues • Older children/adults: Headache, vomiting, lethargy, seizure, neurocognitive symptoms • Infants: Bulging fontanelle, ↑ head circumference, irritability, lethargy • DIAGNOSTIC CHECKLIST • • Consider • Shunt + headache does not always mean shunt failure – Consider sinusitis, trauma, sinovenous thrombosis, viral infection! • Confirm programmable shunt valve setting after MR • Plain film shunt series has extremely low yield in absence of clinical evidence for mechanical shunt failure • Image Interpretation Pearls • Compare with prior studies to detect subtle ventricular size changes • Poor ventricular compliance may prevent change in ventricular size despite florid clinical shunt failure • Fluid tracking along shunt may be only sign of failure, possible even if ventricles normal or unchanged size
  33. 33. THANX