Pseudo Achondroplasia

A recognized form of short-limb dwarfism, body proportions similar to those of Achondroplasia except a normal sized head and normal facial features.

Clinically characterised by normal head size and facial features (Cf Achondroplasia), disproportionately long trunk, rhizomelic shortening of extremities, short stubby fingers. Incomplete elbow extension. Delayed development of the femoral head, resulting in hip dysplasia and a waddling gait. Genu varus deformity of knee. Severe ligamentous laxity (with exception of elbow)

The radiographic features:

in spine platyspondyly, flame-shaped vertebrae with anterior projections. The interpedicular distance does not progressively decrease in the lumbar spine ( Cf. Achondroplasia). Exaggerated  thoracolumbar kyphosis, mild to moderate scoliosis. At CV junction odontoid hypoplasia.

Long bones are short and broad. Both the epiphyses and metaphyses are affected. Flaring of the metaphyses. angulations. Delayed epiphyseal ossification. Epiphyses appear irregular and fragmented.

In joints hips and knees are primarily affected. In hip, shallow acetabulum with hip dysplasia and secondary degenerative changes. Marked dysplasia of the femoral head, short neck of femur. Flattend femoral head may show fragmention. In knee Genu varum deformity.

Short stubby metacarpals.

Normal skull radiograph.

Condition will not become apparent until between 18 and 24 months of age. Manifests itself over time. Ultimately, adult stature is between 82 and 130 cm.

Hydatid cysts brain

A 34 y o male with headache, nausea and vomiting.
Here is his MRI Brain, Axial T2, T1, FLAIR, Diffusion, Post contrast T1w images with MR Spectroscopy.

This MRI study of Brain shows:
Multiple intra axial round to ovoid unilocular cystic signal intensity focal lesions in supra tentorium as well as posterior fossa.
Fluid content of cyst is not very clear as it is hyperintense on FLAIR due to incomplete signal suppression of fluid, debris is seen in dependent portions.
The lesion in posterior fossa show no perilesional odema, lesions in parietal regions show mild odema underneath the lesion (may indicate an associated inflammation or a superadded infection).
None show restricted diffusion on DW images.
No significant mass effect.
Thin uniform thickness wall, non enhancing on post contrast T1w images.
On single voxel MR Spectroscopy at short TE of  35ms from right to left;
At 1.3 ppm - sharp doublets of lactate.
At 2.01ppm - no peak of NAA.
At 3.03ppm - no peak of Creatinine.
At 3.2ppm - no peak of Choline.

Imaging diagnosis : Hydatid cysts. 

Follow up not available.


CEREBRAL HYDATID 

Echinococcus (hydatid disease) affecting the CNS, is caused by E granulosis most commonly and E multilocularis.
Dogs or other carnivores are definitive hosts.
Sheep or cattle are intermediate hosts.
Humans are secondarily infected by ingestion of food or water contaminated with parasite eggs.
Parasite from GI tract to portal system, lymphatics.
Infection usually occurs in liver and lungs.

Typical imaging findings are large uni or multilocular cyst, isodense to CSF on CT and MRI. No edema and enhancement is typical. Fine peripheral enhancement may be seen on MRI. Calcification rare.

DDs
Neoplasm
Primary or metastatic (primary often known)
Thick, irregular margin enhancement typical.
Abscess
T2 hypointense rim and restricted diffusion is typical.
Perilesional odema.
Ring-enhancement.
Porencephalic cyst
Encephalomalacia +/- surrounding gliosis
Typically communicates with ventricle

Clinical presentation
Occur at all ages but commonly affect children and young adults.
Signs and symptoms depend up on location of the lesion.
Lesion develops slowly over many years. May get complicated by rupture, hemorrhage, secondary infection

Treatment
Variable, ranges from oral therapy to lesion resection.

Subdural Empyema

CT and MRI Axial T2 and Diffusion study of brain show diffuse cerebral edema with mild ventriculomegaly. 

Right side mastoiditis.

A thin layer of subdural collection along tentorium and interhemispheric fissure with restricted diffusion is very typical of a Subdural Empyema.

Related post : Subdural-abscess

EMPYEMA 

Syn: Subdural (SDE) or Epidural (EDE) Abscess. 

An extra axial localised collection of pus in sudural or epidural space or both.

SDE is more common than EDE.

Location: 

SDE more common in Supra tenotrium ( Cerebral convexity > interhemispheric fissure > tentorium) than Infratentorium (Cp angle > Cerebellar convexity) 

EDE in Supra tentorium common in Frontal region. 

Imaging findings:

Collection is extra axial cresentic shaped if SD and bi convex shaped if ED.

Density on CT and signal intensity on MR vary depending up on its density and protein content. 

Strong peripheral enhancement on post contrast is must. 

Restricted diffusion on MRI Diffusion is typical and is helpful to rule out other DDs like sub dural hygroma and effusion. 

Clinical Presentation:

Can occur at any age, No gender predominence. 

Often present with headache and fever. May show signs of meningitis. 

Etiology: 

An mastoid or sinus infection present in more than 75%.

Can be a complication of trauma or neurosurgical procedure. 

Prognosis: 

Progress rapidly, fulminant course, a neurosurgical emergency.

Complications and bad prognosis more common in SDE than EDE are CVT, focal cerebritis, Parenchymal abscess, meningitis, Hydrocephalus. Reason is in EDE the tough dura limits the collection and act as barrier between infection and brain. 

Mortality is 10-15%. 

Diagnosis solely based on imaging.

Lumbar puncture can be fatal. Csf examination can be normal. 

Treatment:

Mainly surgical drainage by wide craniotomy followed by patching. 

IV Antibiotics. 

MRI Artifacts : Magic Angle Effect

MRI Sag STIR
An artifactual T2 bright signal seen in tendons and ligaments that are oriented at about a 55 degree angle to the main magnetic field, not to be mistaken for tear.

Signal from water molecules associated with the tendon collagen fibers not normally seen because of dipolar interactions that result in very short T2 Times. At an angle of about 55 degrees to the main magnetic field, the dipolar interactions become zero, resulting in an increase of the T2 Times about 100 fold. This results in signal being visible in tendons. A bright signal from this artifact is commonly seen in the rotator cuff and distal patellar tendon.
Reference : http://www.mritutor.org/mritutor/magica.htm

Medulloblastoma

An 18 yo male with nausea and vomiting.
Here is his Non contrast CT Brain, MRI Brain Axial T1, T2, FLAIR, Diffusion, Post contrast T1w images at the level of posterior fossa with single voxel MR Spectroscopy at TE of 35 ms.

This CT and MRI study of Brain shows:
A well circumscribed ovoid intra ventricular space occupying mass completely occupying and expanding fourth ventricle, leading to mild obstructive hydrocephalus. 

Lesion is solid, hyper dense on CT with spotty calcification at the center.
Signals isointense to cortical gray matter on T1 and FLAIR, slightly hyperintense on T2w images. No cystic component. No marked areas of necrosis. Restricted diffusion on MRI Dw images. Lesion is lobulated, mild heterogeneous enhancement on post contrast T1.
On MR Spectroscopy, no peak of NAA at 2.01ppm, no peak of creatine at 3.02 with long sharp peak of raised choline at 3.2ppm.

Here are MRI Axial T1, T2 and FLAIR images with post contrast T1w images of same patient at the level of lateral ventricles shows multiple discrete enhancing nodules along ependymal lining of lateral ventricles, signal of nodules on MRI are same as that of the posterior fossa mass with same restricted diffusion.

Imaging diagnosis : Medulloblastoma with Csf dissemination. 

Similar post:

Medulloblastoma MR Spectroscopy
Lateral origin medullobastoma


MEDULLOBLASTOMA

Syn: MB, Posterior fossa PNET, PNET – MB,
A highly cellular embryonal cell tumor.
Age group : common in children, ~75% diagnosed by 10 years.
3 times more common in males.

Location:
Intraventricular – 4th ventricular roof is a typical and most common location. A most common posterior fossa tumour in children.
Lateral origin – Cerebellar hemisphere is an atypical location common in older children and adults.

Size vary, average size ranges between 3- 5cm at the time of presentation.
On Non contrast CT, solid 4th ventricle mass, hyperdense, calcifcaiton seen in ~20% cases, small intra tumoural cysts, necrosis in ~50% cases.
On MR signal on T1 iso - hypo intense to cortical grey matter on T1 , iso – hyperintense on T2w and FLAIR. High signal on diffusion attributed to its dense, highly cellular nature.
An associated Obstructive hydrocephalus is common seen in ~ 95% cases.
Usually mild to moderate and homogenous enhancement, may show patchy heterogeneous enhancement due to areas of necrosis.
On MR Spectroscopy, NAA reduced or absent as it’s a non neuronal tumour, raised choline.

Dural AV Malformation / Fistula MRI

MRI Brain Axial FLAIR and coronal T2w images show an extra axial nodular T2 flow voids in right parasellar region, flow related signals on 3D TOF Noncontrast MR Angiography suggestive of a high flow vascular malformation. No direct communication with adjacent right ICA rules out ICA Aneurysm.
It seems to be a Dural Arterio Venous Malformation / Fistula, finding is noted incidentally as pt actually presented for a recent infarct involving cranial portion of right cerebellar hemisphere in superior cerebellar artery territory. 

Bilateral ICA aneurysms MR Angio

This MRI study of Brain Axial T2w images shows:
A right para sellar and a left supra sellar ovoid well circumscribed lesions with T2 flow voids in relation of ICAs, show flow related signals on 3 D TOF Non contrast MR Angiography suggestive of a right ICA cavernous portion and a left ICA supra clinoid portion aneurysm. 

When unilateral ICA aneurysm seen equally distributed on either side. When involve bilateral ICA called mirror aneurysms.

Aggressive Hemangioma MRI Spine

A 55 yo female with compressive myelopathy clinically.

Findings: 

D2 vertebral body and adjacent posterior elements show an abnormal altered marrow signals, heterogeneously hyper intense on T2 and STIR with low signal intensity vertical striations on sagittal sections, multiple punctate low signal intensity dots on Axial T2w sections so called as 'Polka dot' appearance corresponds to coarse, thickened vertical trabeculae characteristic of Spinal Osseous Hemangioma.
An associated anterior epidural lentiform shaped soft tissue causing canal stenosis, anterior displacement of cord with significant cord compression.

Imaging wise diagnosis : Aggressive vertebral Hemangioma.

HISTOPATHOLOGY REPORT

Gross Appearance : The specimen consists of grey brown soft and largely bony fragments together measuring ~ 25x14mm. Representative sections are submitted for processing after de calcifying bone.

Microscopy : A benign neoplasm composed of vascular tubes or spaces lined by endothelium and many containing blood. The interstitial tissue contains a couple of spicules or trabeculae of bone.

Histopathological Diagnosis : Spinal Intraosseous Hemangioma.

Vertebral body hemangioma are usually benign looking and asymptomatic.
Rarely aggressive and pt may present with cord compression due to an associated epidural soft tissue as in this case.

Similar case : Spinal-epidural-lesion-causing-cord compression

Cystic pituitary adenoma

A young male came for evaluation of visual field deficit. Pt was clinically stable.

This MRI study of Brain shows: 

MRI sagittal T1 and T2 w images show a sellar supra sellar oblonged cystic mass.
Cyst is slightly hyper intense than Csf on T1 and iso intense on FLAIR due to lack of signal suppression of fluid implies to thick viscous content of cyst. Thick profusely enhancing wall around cyst on Post contrast T1w images.
No solid component or multilocularity of cyst.
T1 bright normal posterior lobe of pituitary seen stretched along posterior wall of cyst on sagittal non contrast T1w images. Pituitary gland not seen separately in hypophyseal fossa. Pituitary stalk is seen ending at the top of cyst. Supra sellar anatomy distorted. Optic nerve and chiasma compressed.

Imgingwise DDs: Cystic pituitary adenoma more likely than Rathke’s cleft cyst (Thick profusely enhancing wall around cyst goes against Rathke’s cleft cyst).

Transnasal Transphenoid approach attempted.
Histopathology report : Pituitary Adenoma with Necrosis. 

Invasive macroadenoma

This MRI study of brain shows:

A well demarcated ovoid soft tissue signal intensity mass confined to sella seems to be the enlarged pituitary gland itself as pituitary gland is not seen separately in hypophyseal fossa, mild to moderate enhancement on post contrast T1. Both the ICAs are encased. Abnormal marrow signals involving clivus with erosions of floor of hypophyseal fossa. Sphenoid sinus show marked mucosal thickening and soft tissue. No significant mass effect on supra sellar anatomy.

Imagingwise diagnosis : Invasive / Aggressive Macroadenoma.

Tran sphenoid scopy and biopsy attempted, histopathology reports Macroadenoma.