CNS Flashcards
- Which of the following statements are correct about Subarachnoid hemorrhage (SAH): (T/F)
(a) A normal CT within 24 h of onset of symptoms excludes SAH.
(b) The most common etiology is trauma.
(c) Focal interhemispheric blood suggests an anterior communicating artery aneurysm rupture.
(d) Blood in the 4th ventricles is a typical feature of posterior communicating artery aneurysm rupture.
(e) SAH detected on CT more than 1 week after the initial hemorrhage suggests recurrent bleeding.
Answers:
(a) Not correct
(b) Not correct
(c) Correct
(d) Not correct
(e) Correct
Explanation:
A ruptured intracranial aneurysm is the most common aetiology and accounts for 72% of cases of SAH.
A normal CT within 24 hours can exclude SAH in 90% of cases but not always.
4th ventricle blood is common with posterior inferior cerebellar artery aneurysms.
- Regarding subarachnoid haemorrhage: (T/F)
(a) It occurs secondary to arteriovenous malformation in 10% of cases.
(b) It is associated with subdural haemorrhage in 20% of cases.
(c) 15-20% of patients will have multiple aneurysms.
(d) MRI is the best modality for detecting early subarachnoid haemorrhage.
(e) Cerebral vasospasm is maximal from 48 to 72 hours after the event.
Answers:
(a) Correct
(b) Not correct
(c) Correct
(d) Not correct
(e) Not correct
Explanation:
Subarachnoid haemorrhage is associated with subdural haemorrhage in 5% of the cases.
Initially subarachnoid haemorrhage may not be seen on MRI, hence CT is used for earlier detection of subarachnoid haemorrhage.
Cerebral vasospasm occurs at 5-17 days after the event of subarachnoid haemorrhage.
- Concerning the differences between cortical contusions and diffuse axonal injury (DAI): (T/F)
(a) Patients with cortical contusions are much less likely to have had loss of consciousness.
(b) Patients with cortical contusions usually have a better prognosis.
(c) Cortical contusions are more commonly haemorrhagic than DAI.
(d) CT is the best modality to diagnose acute DAI.
(e) Most patients with DAI suffer immediate loss of consciousness.
Answers:
(a) Correct
(b) Correct
(c) Correct
(d) Not correct
(e) Correct
Explanation:
Diffuse axonal injury are seen much better on MRI than CT. On MRI diffusion weighted images and susceptibility weighted images are most
- Which of the following statements are correct about Haemangioblastoma (HB): (T/F)
(a) The most common site is the spinal cord.
(b) Is the most common primary cerebellar tumor in adults.
(c) Most patients with multiple HBs have von Hippel-Lindau disease
(d) Most HBs have homogeneously solid appearance on MRI.
(e) Most HBs do not enhance after intravenous gadolinium.
Answers:
(a) Not correct
(b) Correct
(c) Correct
(d) Not correct
(e) Not correct
Explanation:
HB is a vascular tumour of the CNS. It occurs most often in the cerebellum, where it is the most common primary neoplasm in adults.
HBs are less commonly seen in the spinal cord and rarely occur elsewhere in the CNS.
Cerebellar hemangioblastomas are traditionally classified into 4 types.
Type one is a simple cyst without macroscopic nodule.
Type II (most common) is a cyst with a mural nodule.
Type III: solid tumours
& type IV: solid tumours with small internal cysts.
- Which of the following statements are correct about pineal region masses: (T/F)
(a) Pineoblastomas are categorised as part of the primitive neuroectodermal tumour group.
(b) Pineoblastomas usually show poor enhancement.
(c) Germinomas are 10 times more common in males than females.
(d) Pineal germinomas are associated with Parinaud’s syndrome.
(e) Germinomas are hypodense on unenhanced CT.
Answers:
(a) Correct
(b) Not correct
(c) Correct
(d) Correct
(e) Not correct
Explanation:
Pineoblastomas show avid enhancement on post contrast images.
The isodense to hyperdense on CT.
They are similar to medulloblastoma as the both are part of neuroectodermal tumour group.
- Regarding differentiation between epidermoids and dermoids of the brain: (T/F)
(a) Epidermoids more closely resemble cerebrospinal fluid on MRI.
(b) Both are formed due to enclosure of ectodermal elements when the neural tube closes.
(c) Epidermoids are more common.
(d) Epidermoids may become malignant.
(e) Fat-fluid level on imaging is highly suggestive of dermoids.
Answers:
(a) Correct
(b) Correct
(c) Correct
(d) Not correct
(e) Correct
Explanation:
Dermoids and epidermoids are benign lesions and slow-growing and never become malignant.
- Concerning cerebellopontine angle masses: (T/F)
(a) Meningiomas are the second commonest cerebellopontine angle mass.
(b) Meningiomas commonly cause expansion of the internal auditory canal.
(c) Meningiomas are typically brighter on T2 weighted MRI than T1.
(d) Epidermoids have the same signal as cerebrospinal fluid on MRI.
(e) Acoustic neuromas usually enhance poorly on post-contrast scans.
Answers:
(a) Correct
(b) Not correct
(c) Not correct
(d) Correct
(e) Not correct
Explanation:
Meningiomas do not cause expansion of internal auditory canal.
They are usually less bright on T2-weighted MRI.
Acoustic neuromas usually enhance avidly on postcontrast images.
- Which of the following statements are correct about cerebellar medulloblastoma: (T/F)
(a) Is more common in females.
(b) Is the commonest paediatric brain tumour.
(c) 75% of patents are less than 15 years of age.
(d) Calcification occurs in 40-50%.
(e) Is associated with basal cell carcinomas.
Answers:
(a) Not correct
(b) Not correct
(c) Correct
(d) Not correct
(e) Correct
Explanation:
Medulloblastoma is the second commonest paediatric tumour, second only to astrocytoma however it is the commonest paediatric posterior fossa tumour.
It occurs more commonly in males.
Calcifications are seen in up to 20% of patients.
Cystic changes or necrosis are seen in up to 50%.
They are usually hyperdense on CT. On MRI, they are usually hypointense to grey matter on T1 images and variable appearance on T2-weighted images. Oedema is almost always seen.
- Concerning intracranial lymphoma: (T/F)
(a) It is usually a Hodgkin’s lymphoma.
(b) Secondary lymphoma more commonly involves the leptomeninges than the brain parenchyma.
(c) It is usually hypodense on unenhanced CT.
(d) It is normally high signal on T2 weighted images.
(e) Toxoplasmosis may mimic lymphoma in the brain.
Answers:
(a) Not correct
(b) Correct
(c) Not correct
(d) Not correct
(e) Correct
Explanation:
CNS lymphoma are usually B-cell non-Hodgkin’s lymphoma.
They are usually hyperdense on unenhanced CT.
There show intermediate to low signal on T2-weighted MR images.
- Concerning posterior fossa tumours in children: (T/F)
(a) 80% of medulloblastomas arise from the vermis.
(b) Juvenile pilocytic astrocytomas are the second commonest posterior fossa tumour.
(c) Juvenile pilocytic astrocytomas usually calcify.
(d) Brainstem gliomas mostly affect the midbrain.
(e) Ependymoma seeds to the CSF in 30% of cases.
Answers:
(a) Correct
(b) Correct
(c) Not correct
(d) Not correct
(e) Correct
Explanation:
Juvenile pilocytic astrocytomas are at the second commonest posterior fossa tumours after medulloblastoma. Only 20% of these calcify.
Brainstem gliomas mostly affect the pons.
- Which of the following are correct regarding dermoid and epidermoid cysts? (T/F)
(a) Epidermoid cysts are usually unilocular.
(b) High signal on T1 weighted MRI is diagnostic of a dermoid cyst.
(c) Dermoid cysts may be distinguished from lipoma on T1 weighted MRI.
(d) The most common location of dermoid cyst in the head and neck is the orbit.
(e) Epidermoid cysts have high signal on T2 weighted MRI scans.
Answers:
(a) Correct
(b) Not correct
(c) Not correct
(d) Correct
(e) Correct
Explanation:
Dermoid cysts are usually hyperintense on T1-weighted MR images but this signal characteristic can be seen in other lesions example lipoma.
Hence their differentiation is not recommended on T1-weighted MR images.
Dermoid cysts are usually seen in orbit, oral and nasal cavities however orbit is the most common site.
- Characteristic features of Herpes simplex encephalitis (HSE) in adults include: (T/F)
(a) Unilateral cerebral involvement
(b) Infection by HSV type II
(c) Untreated infection has a mortality rate of 50-70 %
(d) Gyriform enhancement on contrast enhanced CT
(e) High signal in the cingulated gyrus on T2W MRI.
Answers:
(a) Not correct
(b) Not correct
(c) Correct
(d) Correct
(e) Correct
Explanation:
Neonatal herpes is caused by HSV II and herpes in adults is caused by HSV I. In adults, herpes initiates as unilateral involvement of limbic system ( temporal bones, insular cortex, subfrontal area and cingulated gyri) but eventually follows bilaterally. CT performed early in the course of illness may be normal or only subtly normal.
- Which of the following statements are correct about Pyogenic brain abscesses: (T/F)
(a) Most commonly occur secondary to a generalised septicaemia.
(b) Typically occur at the corticomedullary junction.
(c) On CT have a smooth regular wall with relative thinning of the lateral wall.
(d) Are more common in the occipital lobes than the frontal lobes.
(e) The most common causative organism is Staphylococcus.
Answers:
(a) Not correct
(b) Correct
(c) Not correct
(d) Not correct
(e) Not correct
Explanation:
32% of the pyogenic brain abscesses could be due to generalised septicaemia for example, from a lung abscess or pneumonia. However 41% occur secondary to extension from paranasal sinus infection.
The occur most commonly in the frontal lobes than in the occipital lobes.
On CT there is a relative thinning of the medial wall due to would blood supply of white matter which leads to the rupture of the abscess into the ventricular system.
Most common causative organism is streptococcus.
- Concerning differences between primary CNS lymphoma and toxoplasmosis: (T/F)
(a) Subependymal extension across the corpus callosum is more likely to occur in toxoplasmosis.
(b) High signal on T2 weighted MRI favours lymphoma.
(c) Toxoplasmosis is more frequently multiple.
(d) Ring enhancement following contrast administration favours lymphoma.
(e) The lesions are usually smaller in lymphoma.
Answers:
(a) Not correct
(b) Not correct
(c) Correct
(d) Not correct
(e) Not correct
Explanation:
CNS lymphoma shows subependymal extension across the corpus callosum.
CNS lymphoma and toxoplasmosis lesions can be smaller as well as large and should not be differentiated on basis of size.
Toxoplasmosis shows high signal on T2-weighted MRI and shows ring enhancement on post contrast images.
- Which of the following statements are correct about MRI features of multiple sclerosis: (T/F)
(a) Corpus callosum lesions are best visualized on axial view.
(b) T2W spin echo is superior to FLAIR for posterior fossa lesions.
(c) Whiter matter lesions are more conspicuous than grey matter lesions.
(d) Ring enhancement on post gadolinium T1W MRI suggests an alternative diagnosis.
(e) 10-15 % of patients have lesions limited to the spinal cord.’
Answers:
(a) Not correct
(b) Correct
(c) Correct
(d) Not correct
(e) Correct
Explanation:
MS plaques are classically seen in periventricular and juxtacortical white matter. Involvement of corpus callosum is characteristic and is best seen on Sagittal images. Both solid and ring enhancement may occur. Incomplete ring enhancement is seen in larger MS plaques.
