Hypoxic ischaemic brain injury

In evaluation of hypoxic ischaemic brain injury,
1. Diffusion weighted images are more sensitive than MR spectroscopy in acute setting
2. Most of the germinal matrix haemorrhage occur within 24 hours of birth
3. Cerberal cortex is more often involved in hypoxic injuries than deep grey structures in neonates and pre-term babies
4. Normal appearance on diffusion weighted images by the end of first week of hypoxic insult indicates reversal of hypoxic insults
5. Germinal matrix haemorrhage extending into ventricles is graded as IV

Answers: F, T, F, F, F

Notes: Diffusion weighted images are more sensitive than T1 and T2 weighted images, but MR spectroscopy is more sensitive than diffusion weighted images. MRS shows increased lactate in the deep gray matter, parieto-occipital region, and watershed zones as early as 2-8 hours. Germinal matrix haemorrhage is more often seen in pre-term babies born weighing less than 2000g and majority of the bleeds occur within 24 hours of birth. Deep grey structures are more often involved than cerebral cortex in both neonates and pre-term babies. Thalami, anterior vermis and dorsal brainstem are more frequently involved in pre-term babies, where as in full term neonates basal ganglia are more often involved. Diffusion-weighted images, although sensitive in diagnosing hypoxic damage, but they often underestimate the extent of the injury. Diffusion-weighted images also tend to normalise by end of the 1st week, but do not imply reversal hypoxic insult (pseuonormalization). Germinal matrix haemorrhages are graded into: Gr1 – subependymal haemorrhage without or minimal intraventiruclar bleed; gr 2 – germinal matrix and intraventricular haemorrhage without ventricular dilatation; gr 3 – gr 2 + ventricular dilatation; gr 4 – periventricular parenchymal haemorrhagic infarct

Reference: Huang BY et al. Hypoxic-Ischemic Brain Injury: Imaging Findings from Birth to Adulthood. RadioGraphics 2008;28:417-439

Limbic encephalitis

Regarding limbic encephalitis (LE),

1. Usually presents with long term memory impairment
2. MRI typically shows high signal on T2 and FLAI in the limbic region
3. The most common underlying malignancy is small cell lung cancer (SCLC)
4. PET is useful in diagnosing underlying occult malignancy

Answers: F, T, T, T,

Notes: LE usually presents with short term memory impairment, seizures, confusion and psychiatric symptoms. Brain stem may also be involved. LE can be paraneoplastic or non-paraneoplastic. SCLC is the most common cause; other causes include testicular cancer, ca breast, teratoma, HL, thymoma. Although LE can be idiopathic, underlying malignancy should be searched.

Reference:
Rutherford GC et al. Imaging in the investigation of paraneoplastic syndromes. Clinical Radiology Volume 62, Issue 11, November 2007, Pages 1021-1035

Tuberculosis

Regarding tuberculosis,

1. Radiographic evidence of hilar lymphadenopathy is more common in adults than in children
2. Cavitation is hallmark of post-primary TB
3. In TB meningitis, abnormal meningeal enhancement is more often seen in the basal cisterns
4. In spinal TB, calcification of abscess is characteristic
5. Calcification is seen more than 50% of renal TB

Answers: F, T, T, T, T

Notes: Radiographic evidence of lymphadenopathy is more common in children (96%) than in adults (46%) and more often seen in the right hilar and right paratracheal location. Cavitation is hallmark of post-primary TB, where as lymphadenopathy is rare (5%). Calcification of abscess is highly specific of TB spine. In renal TB, calcification is seen in more than 50% and the other findings include calcyceal deformity and papillary necrosis.

Reference: Burrill J et al. Tuberculosis: A Radiologic Review. RadioGraphics 2007;27:1255-1273

Hypothalamus

Regarding hypothalamic lesions,

1. Craniopharyngioma are typically predominantly cystic in adults
2. Hypothalamic germinomas typically involve base of the infundibular stalk
3. Hypothalamic hamartomas usually show no change in size on long term follow-up
4. Hypothalamic-chiasmatic gliomas are strongly associated with NF-1
5. Dynamic MRI is helpful in differentiating LCH from germinoma

Answers: F, T, T, T, F

Notes:
Craniopharyngiomas (CP) have a bomodal presentation; the paediatric CPs are typically solid and cystic (adamantinomous type) and the adult CPs are perdominantly solid (papillary).
Hypothalamic germinomas present in childhood and teens; synchronous lesions in pineal region are seen in 10%; typically seen in the base of the infundibular stalk and show homogenous contrast enhancement.
Hypothalamic hamartomas usually present by 10-20 years, boys being more commonly affected; present with precoucious puberty or gelastic seizures; sesille ot pedunculated isointense lesionsin tuber cinerium; do not change in size and signal at long term follow-up.
Hypothalamic-chiasmatic gliomas are paediatric tumors (2-4 years) and up to 50% have a family history of NF-1.
On dynamic MRI, germinomas, LCH and hemangioblastomas show gradual increase in enhencement without washout; adenohypophysitis showssharp increase in curve with steep washout.

Reference:
Saleem SN et al. Lesions of the Hypothalamus: MR Imaging Diagnostic Features. RadioGraphics 2007;27:1087-1108

Sickle cell disease

Regarding sickle cell disease,

1. The most common cause of death is stroke
2. Intracranial anuesysms associated with sickle cell disease are usually single
3. Moya moya is characterictic of sickle cell disease
4. "hair-on-end"appearance on the skull radiograph is characteristic feature of sickle cell disease
5. The most common cause of osteomyelitis is salmonella

Answers: F, F, F, F, T

Notes:
The most common cause of death in sickle cell disease (SCD) is pulmonary complications. Children with SCD are 100 times more risk for pneumonias. Acute chest syndrome is more lethal in adults than children. The most common complication in brain are stroke, ischemia and atrophy. 11% have stroke by the age of 20 years. Infarcts are common in children and haemorrhage in adults. Moyamoya is secondary to large vessel occlusion with telangiectactic colateral circulation and seen in SCD, tuberous sclerosis, neurofibromatosis, vasculitides, infection. Intracranial anuerysms associated with SCD are usually multiple (57%) and 30% are seen in posterior circulation.

"Hair-on-end" appearance is seen in any anaemia. SCD patients are prone for bone infarcts and osteomyelitis, especially from salmonella. Osteomyelitis most commonly affects diaphysis of long bones.

Reference:
Madani G et al. The radiological manifestations of sickle cell disease. Clinical Radiology. Volume 62, Pages 528-538

Melanoma

Regarding imaging of melanoma,

1. Majority of the melanoma metastasis to brain are hyperdense on unenhanced CT scan
2. Melanoma metastasis in brain usually show high signal on both T1 and T2
3. Most of the intraocular melanomas are metastatic
4. Lung metastasis is relatively common
5. Most of the bone metastasis are osteolytic

Answers: T, F, F, T, T

Notes: Most of the melanoma metastasis to brain are multiple, occur at corticomedullary junction and 85% are hyperdense on unenhanced CT scan. Hemorrhage is found in nearly 20%. On MR, they are typically high signal on T1 and low on T2. Most of the intraocular melanomas are primary and ultrasound and MRI are used in the evaluation of the lesion. 40% of lung metastasis are multiple, 20% solitory, 7% adenopathy and 28% combination of these. Bone metastasis is also relatively common and seen in 23% of ocular melanomas. The most common site is spine and most are lytic.

Reference: Kalkman E et al. Melanoma. Clin Rad 59 (2004): 313-326

Neuroimaging in HIV/AIDS

Regarding toxoplasma encephalitis in HIV/AIDS, (***)

1. Toxoplasma encephalitis is more common than HIV encephalitis
2. Toxoplasma is the most common opportunistic neuroinfection in AIDS
3. Toxoplasma encephalitis preodominantly involves periventricular white matter
4. The more the nodular or ring enhancement, the more is the CD count
5. On an unenhanced CT scan, the lesions are usually hypodense

Answers: F, T, F, T, F

Notes: HIV encephalitis accounts for up to 60% with AIDS, where as toxoplasma encephalitis accounts for approximately 30% of cases. Toxoplamosis, being the most common opportunistic neuroinfection, may result in necrotising encephalitis, predominantly involving the basal ganglia and thalami. On Unenhcened CT, the lesions are usually isodense to grey matter, but may be hyperdense due to hemorrhage and on contrast, usually show ring or nodular enhancement. Faint or absent enhancement is seen if the CD count is less than 50 and the enhancement increases with increase in the CD count.

Regarding neuroinfections in HIV/AIDS,

1. HIV encephalitis preferentially shows white matter changes in the centrum semiovale
2. CMV encephalitis usually involves brain stem and periventricular white matter
3. CMV encephalitis typically heals by periventricular calcifications
4. Cryptococcus usually causes ring enhancing lesions in the basal ganglia
5. PML (progressive multifocal leucoencephalopathy) typically shows mass effect and contrast enhancement

Answers: T, T, F, F, F

Notes: Demyelination and gliosis in HIV encephalitis affects deep white matter, preferentially involving the centrum semiovale. CMV cause meningoencephalitis with predominant involvement of periventricular white matter and brain stem, ventriculitis, infarcts, spinal cord, cranial nerves. CT may show diffuse white matter hypodensity and on contrast, may show ependymal, ring or nodular enhancement. Periventricular calcification is a sign of congenital CMV infection and not a feature of CMV infection in immunocompromised. Cryptococcus is the most common fungal infection in AIDS and typically causes meningitis. PML is caused by Gr B papovavirus and shows bilateral pathy white matter abnormality without mass effect or contrast enhancement.

Reference:Offiah et al. The imaging appearances of intracranial CNS infections in adult HIV and AIDS patients. Clinical Radiology (2006) 61: 393-401

Traumatic diaphragmatic rupture

Regarding traumtic diaphragmatic rupture (TDI),

1. TDIs most commonly occur after penetrating trauma
2. Left diaphragm is more commonly ruptured than the right
3. About 50% of TDI are diagnosed acutely
4. The most commonly herniated organ is spleen
5. 'Dependent viscera sign' is a very sensitive CT sign in the diagnosis of TDI

Answers: F, T, F, F, T
Notes: TDIs commonly occur after blunt trauma as in RTA or fall. Because of the liver, the right hemidiaphragm is ruptured less common than the left. Only about 10% of TDIs are diagnosed in acute setting. Stomach is most commonly herniated organ (32%), followed by colon (27%). CT is investigation of choice even in the acute setting. 'Dependent viscera sign' on CT is very sensitive in the diagnosis of TDI. The bowel or abdominal viscera usually do not contact the ribs due to seperation by diaphragm; contact indicates diaphragmatic injury and is known as 'dependent viscera sign'. Sagittal reconstruction is most sensitive and specific in the diagnosis of TDI.
Reference:

1. Eren S et al. Imaging of diaphragmatic rupture after trauma. Clin Rad (2006)61, 467-477
2. ABCs of blunt trauma

Central Neurocytoma

Regarding central neurocytoma (CN),

1. CN are typically located within the fourth ventricle.
2. Light microscopic appearance is similar to meningioma.
3. Most of the CNs present after 60 years of age.
4. The attachment to the lateral wall of the lateral ventricle is charactersitic for CN.
5. Intratumoral calcification is rare.

Answers: F,F, F, F, F
Notes: CNs are typically located within the lateral ventricle with extension into the third ventricle. The light microscopic features are similar to oligodendroglioma (OD) and many CNs were diagnosed as ODs in the past; hence immunohistochemistry with synaptophysin should be done. Most of the CNs present between 20 and 40 years with no sex prevelance. Attachment to the spetum pellucidum is considered as characteristic for CN. CNs are typically low on T1, high on T2 with usually some enhancment. Intratumoral calcification is common, where as haemorrhage is rare. Differentials include choroid plexus paiplloma, astrocytoma, meningioma, ependymoma, subependymoma and oligodendroglioma.
Reference: Zhang et al. Central neurocytoma: clinical, pathological and neuroradiological findings. Clin Rad (2006): 61: 348-357 .