Bone infarct - MRI

Bone infarct is ischemic death of the cellular elements of the bone and marrow in metaphysis and diaphysis. Lesions in the epiphysis are called avascular necrosis (AVN). Presently the term osteonecrosis is accepted and used widely.

Causes: Idiopathic, Trauma, Idiopathic causes such as Legg-Calvé-Perthes disease, Renal transplantation, Increase in endogenous steroid levels, as in patients with Cushing syndrome, Collagen vascular disorders such as systemic lupus erythematosus (SLE), rheumatoid arthritis, and scleroderma, Hemoglobinopathies such as sickle cell disease and thalassemia, Hemophilia, Gaucher disease, Fabry disease, Infection, Pancreatitis, Pregnancy, Gout and hyperuricemia, Diabetes, Use of immunosuppressants and other drugs such as exogenous steroids, indomethacin, and phenylbutazone, Alcohol use, Dysbaric osteonecrosis, Radiation therapy, Arteritis.

Imaging:

Radiograph: Findings are characteristic in established case. Early stages radiograph is not of much use. In the epiphysis region, an arc like, subchondral, lucent lesion may be associated with areas of patchy loss of bone opacity intermingled with sclerotic areas and bone collapse. In the diametaphyseal region, a sheet like lucency of varying size is usually surrounded by shell-like sclerosis and/or calcification and periostitis. In flat or complex bones, patchy lucencies and sclerosis are often associated with bone collapse or fractures.

Steinberg has classified the radiologic appearance into 6 stages, as follows¹² :

• Stage 0 - Normal findings are demonstrated.
• Stage I - The appearance may vary from normal to subtle trabecular mottling, but an isotopic bone scan or MRI shows abnormal bone.
• Stage II
• Stage IIa - Focal radiopacity is associated with osteopenia.
• Stage IIb - Radiopacity is associated with osteoporosis and an early crescent sign.
• Stage III
• Stage IIIa - An established crescent sign is associated with cyst formation.
• Stage IIIb - Mild alteration in the configuration of the femoral head is caused by a subchondral fracture, but the joint space is maintained.
• Stage IV - Marked collapse of the femoral head is demonstrated with an associated acetabular abnormality.
• Stage V - Joint space narrowing is demonstrated with changes of secondary osteoarthrosis.

CT scans: Central or peripheral areas of reduced attenuation. Reformatted sagittal and coronal images show subchondral fractures and collapse of the articular surface. May show subtle trabecular irregularity associated with bone necrosis in early stages.

MRI: Ischemic bone changes become apparent in hematopoietic tissues on MRIs within 6-12 hours. MRI characteristics of bone infarction are patchy areas of low signal intensity on T1-weighted spin-echo images. Diffuse abnormal signal intensity may be present in osteonecrosis of the femoral head; these changes are reflected on both T1- and T2-weighted images.

The most characteristic appearance is the double-line sign, which consists of a hyperintense inner ring and a hypointense outer ring, on T2-weighted MRIs. This finding reflects the reactive interface between ischemic and non ischemic bone. 

Achilles Tendonitis - MRI

46 Year old male with pain in the left ankle MRI T2 FS sagittal and T2 FSE axial images showing diffuse hyperintensities in the distal Achilles tendon with mild marrow edema in the calcaneous at the insertion site and mild peritendinous inflammatory changes suggestive of Achilles Tendinitis.

DISCUSSION:

Tendinitis develops insidiously after sudden changes in activity or training level, use of inappropriate footwear, or training on poor running surfaces, especially if high-risk factors are present (Eg, age, cavus feet, tibia vara, heel and forefoot varus deformities).

Achilles tendon injuries may be classified as:

Tendonitis: Overuse of the Achilles tendon can cause inflammation that can lead to pain and swelling.

Tendinosis: Usually, this injury is an asymptomatic, noninflammatory, degenerative disease process (mucoid degeneration). The patient may complain of a sensation of fullness or a nodule in the back of the leg.

A Thompson test is performed to detect rupture of the Achilles tendon. In this test, the patient lies face downward on the examining table with bent knees and the doctor squeezes the back of the lower leg (calf). If the Achilles tendon is at least partially intact, this test causes the foot to flex.

IMAGING TESTS:

Radiographs: May detect soft tissue thickening and fractures if any associated.

Ultrasound may be usefull to detect thickening of the Achilles tendon and peritendinous collection.

MRI of tendonitis show diffuse for T2 hyperintensity within the tendon and inflammatory changes around the tendon with or without peritendinous collection. My show mild enhancement on contrast study.  Focal T2 hyperintensities seen at the tendon insertion suggestive of insertional tendinitis.

MRI helps to differentiate tendonitis from tendinosis and partial/complete tendon rupture. In tendinosis there will be only tendon degenerative changes without inflammatory changes around the tendon.

TREATMENT: Resting the tendon to allow the inflammation to settle down.

Cholesteatoma- HRCT

Non contrasted temporal bone CT reveals a soft tissue mass in the right middle ear and Prussak’s space with associated erosions of the scutum, epitympanum walls, lateral semicircular canal, tegmen tympani and middle ear ossicles. It is also extending in to the mastoid air cells.

Discussion:

• An acquired cholesteatoma is a collection of exfoliated squamous epithelium and debris.
• Cholesteatomas often begin at the pars flaccida of the tympanic membrane and grow in Prussak's space of the temporal bone and produce inflammatory reaction.
• Cholesteatomas typically occur in the setting of chronic dysfunction of the Eustachian tubes and recurrent otitis media.
• Cholesteatomas can be as small as a couple of millimeters in size or can grow to fill the entire middle ear.
• Erosions of the scutum and ossicles are commonly seen.
• The presence of bony erosions or expansion are strong support of cholesteatoma over chronic otomastoiditis.
• Acquired cholesteatomas occur in children and adults.
• Most common presenting symptoms include ear discharge, hearing loss, ear pain and vertigo.
• Without treatment cholesteatomas will progressively increase in size.
• Complications include: Hearing loss, CN 7 palsy, venous sinus thrombosis, semicircular canal fistulas, and intracranial invasion.
• Early surgical intervention usually results in complete eradication and preservation of hearing.

Differential diagnosis:

1. Acquired cholesteatoma
2. Chronic otomastoiditis
3. Middle ear cholesterol granuloma
4. Glomus tympanicum paraganglioma

Double left renal artery - CT Angiography

44 Year old female referred for CT renal angiography for transplant donor evaluation. The coronal volume rendering images showing normal bilateral kidneys with single right renal artery and two renal arteries on the left side.

Discussion:
CT angiography is the most preferred investigation for donor kidney evaluation since it gives excellent anotomical depiction of the vessels, organs and the function of kidney in urography.
Protocol - Arterial phase, Venous phase and Excretory phase.
The things to be mentioned in the radiological report are

• Size, shape and position of the kidneys.
• Number of renal arteries, any accesory artery.
• Course of left renal vein retroaortic /preaortic.
• Distance of renal artery from origin to first branching.
• Length of right renal vein.
• Any other normal varuients/renal masses.
• Collecting system - Duplication of any.

All these findings are valuable to the graft harvesting surgeon and for the transplant anastomosis.

The Azygos Lobe

55 year old male came with history of chronic cough and was reffered for CT scan to ruleout tuberculosis and any other lung disease. CT scan axial section (first image) shows a azygos vein is coursing through the apical segment of the right upper lobe (arrow). Coronal reformated image shows pleural reflection - mesoazygos (arrow) with azygos vein (arrow head) in the right apical region.

Discussion:

The azygos lobe is a rare anomaly that developmentally arises when the right posterior cardinal vein penetrates the apex of the lung, instead of passing over it, and travels inferiorly taking pleural layers with it to entrap a portion of the right upper lobe. The two folds of pleura form the mesoazygos, a fissure visible on 0.4% of chest radiographs and 1.2% of high resolution computed tomography (CT) studies. The right azygos lobe is supplied by the medial segments of the apical and anterior or posterior branches of the apical segmental bronchial artery and vein. A true left azygos lobe has also been reported.
On chest radiography, the azygos lobe is usually distinguished by the azygos fissure, which superiorly has a triangular shape and inferiorly demonstrates the azygos vein as a tear-shaped shadow. The azygos fissure typically appears as a fine, convex line that crosses the apex of the right lung. The azygos lobe can appear opaque and be incorrectly interpreted as a pathologic mediastinal finding on PA chest radiographs.
When findings on traditional imaging are not clear, CT exams can be helpful in delineating relevant anatomy. Clinically, the knowledge of azygos lobe anatomy is important during thoracic surgical approaches. Partial obstruction of the thoracoscopic view during a bilateral sympathectomy was reported during attempted mobilization of the azygos lobe. Others reported difficulty reflecting the pleura during primary repair of the esophageal atresia in a pediatric patients. There are also reports of the phrenic nerve coursing within the azygos fissure. Finally, multiple authors have reported spontaneous pneumothorax associated with the azygos lobe in both the adult and the pediatric patient.

Adrenal Myelolipoma - CT

CT scan of a 25 year old female showing well defined fat containing lesions seen in the region of right adrenal gland (arrow) suggestive of adrenal myelolipoma.

Adrenal myelolipoma is an uncommon, benign, endocrinologically inactive tumor of unknown pathogenesis composed of adipose and myeloid tissue. Majority of the lesions are detected incidentally. In most lesions, the fatty component is predominant and is recognizable on radiologic images. Such lesions are radiolucent on radiographs, hyperechoic on sonograms, have low attenuation on CT scans, and have bright signal intensity on T1 -weighted MR images and intermediate signal intensity on T2- weighted MR images.

Tumors composed primarily of myeloid tissue may be hypoechoic on sonograms and will have the imaging characteristics of red marrow on other kinds of images. In complicated cases in which infarction or hematoma is present, the margins of the lesions may be irregular and infiltrative, with blood dissecting through the retroperitoneum. The imaging findings of acute, subacute, or chronic hematoma will then be superimposed on the lesion. When lesions are fatty, well marginated, uncomplicated, and in the position of the adrenal gland, a specific radiologic diagnosis is possible. However, the mere presence of fat in an adrenal mass is insufficient for diagnosis, because a metastasis or other aggressive lesion may engulf fat as it spreads. Nonspecific calcification may sometimes present.

Disseminated tuberculosis - CT

Disseminated tuberculosis (TB) is a contagious bacterial infection that has spread from the lungs to other parts of the body through the blood or lymph system. The differential diagnosis of miliary nodules in bilateral lungs are tuberculosis, metastases, sarcoidosis, lymphoma, hypersensitivity pneumonitis and rare causes like silicosis, beryliosis, stanosis. Depending imaging findings and patients clinical deatils, one can differentiate each other.

The differential diagnosis of patients with fever, splenomegaly, and multiple hypoechoic hypoattenuating splenic lesions includes splenic abscesses that may be bacterial, fungal, or granulomatous in nature. Pyogenic abscesses are usually solitary. On US images, they appear as small irregular hypoechoic lesions that may evolve into a poorly defined heterogeneous mass. On CT images, they typically appear as single irregularly marginated hypoattenuating lesions. The presence of intralesional gas is pathognomonic of pyogenic infection, although it occurs infrequently. Multiple splenic abscesses, usually smaller than 2 cm in diameter, are commonly associated with nonbacterial infections (ie, fungal and granulomatous infections). Fungal abscesses, when visible, characteristically appear on US images as round hypoechoic lesions with a central hyperechoic area (ie, “bull's-eye” or “target” appearance) that corresponds to inflammatory cells with a surrounding hypoechoic band of fibrosis. The “wheel-in-a-wheel” pattern is seen when the central portion becomes necrotic and hypoechoic. Contrast-enhanced CT typically depicts fungal splenic abscesses as multiple small low-attenuation lesions. Patients with cat-scratch disease may also develop splenomegaly and splenic microabscesses. Neoplasms that involve the spleen—such as lymphoma (both Hodgkin and non-Hodgkin lymphoma), leukemia, metastasis, or even Langerhans cell histiocytosis—may manifest as focal hypoechoic hypoattenuating lesions. Sarcoidosis, which is a systemic granulomatous disease of unknown origin, may also have abdominal involvement with lymphadenopathy and hypoattenuating nodules in the liver and spleen. It is generally impossible to differentiate visceral TB lesions from fungal infections, lymphoma, or metastasis—unless they are associated with other typical abdominal TB findings, such as lymph node or bowel involvement.

Oriental cholangitis - MRI

42 year old female came with history of recurrent attacks of abdominal pain, fever, and jaundice. MRCP coronal HASTE image of upper abdomen shows dilatation of intrahepatic biliary radicles and CBD with multiple calculi within the hepatic ducts (L>R) and CBD (arrows). No calculi in the gall bladder. Thick slab MRCP image (left) better shows the IHBR and CBD dilatation with hepaticolithiasis and choledocholithiasis. Incidentally note the right retrocaval ureter.

Recurrent pyogenic cholangitis (RPC) or Oriental cholangiohepatitis is a recurrent and chronic and biliary tract infectious process typically seen in the Asian population, particularly Chinese. The disease involves recurrent episodes of infectious cholangitis with fever, abdominal pain, and jaundice. The causative infectious agents are typically bacterial such as E. coli and other coliforms. However biliary tract parasites such as Ascaris lumbricoides and Clonorchis sinensis are common coexistent pathogens, and it is not clear which infectious agents are the primary cause or representative of secondary superinfection.

The recurrent infections lead to bile duct dilatation, strictures, obstruction, and calculi. The bile duct dilatation may be pronounced and involves both the intrahepatic and extrahepatic ducts. There is a predilection for ductal involvement in the left lobe of the liver but diffuse intrahepatic disease can be seen. The extrahepatic bile duct can be quite dilated up to as much as 3-4cm in diameter. The dilatation of the extrahepatic duct may be secondary to loss of elasticity of the duct wall due to chronic infection or it may be due to ampullary narrowing.

The calculi are typically bile pigment stones with varying amounts of calcium. The stones have a mud or paste-like consistency. The stones presumably form due to bacterial enzymes causing deconjugation of bilirubin which then precipitates as calcium bilirubinate. In addition it has been postulated that a low protein diet as is seen in some Asian populations may play a role in formation of intraductal stones. MRCP is gold standard non invasive investigation for diagnosis of oriental cholangitis.

Crohn's disease - CT Enteroclysis

24 year old female came with history of diarrhea and pain abdomen. CT enteroclysis shows significant concenteric wall thickening in the descending colon.

Crohn's disease (also known as Crohn-Lesniowski Disease, or "Charlotte Forditis" morbus Lesniowski-Crohn, granulomatous colitisand regional enteritis) is an inflammatory disease of the intestines that may affect any part of the gastrointestinal tract from anus to mouth, causing a wide variety of symptoms. It primarily causes abdominal pain, diarrhea (which may be bloody), vomiting, or weight loss, but may also cause complications outside of the gastrointestinal tract such as skin rashes, arthritis and inflammation of the eye.

The first investigation to be done in suspected case of chrons disease is barium study, Ba meal follow through and barium enema. Barium study shows bowel luminal narowing and proximal dilatation. Multiple areas of narrowing may be seen in the small and large bowel. Cross sectional imaging mainly CT and MRI (CT&MRI Enteroclysis) are done to analyze specifically for the presence and character of a pathologically altered bowel segment (wall thickness, pattern of attenuation, degree of enhancement, length of involvement), stenosis and prestenotic dilatation, skip lesions, fistulas, abscess, fibrofatty proliferation, increased vascularity of the vasa recta (comb sign), mesenteric adenopathy, and other extraintestinal disease involvement. The normal thickness of the wall of the small intestine and colon is 1–2 mm and 3 mm, respectively, when the lumen is distended. Any portion of the bowel wall that exceeds 4–5 mm is considered abnormal. Bowel wall thickening, usually ranging from 1–2 cm, is the most consistent feature of Crohn disease on cross-sectional images. Mural stratification (“target” or “double halo” appearance) is often seen in active lesions, particularly after the intravenous administration of contrast medium. An inflamed bowel wall demonstrates marked enhancement after intravenous contrast material injection, and the intensity of enhancement correlates with the degree of inflammatory lesion activity.

Bronchocele - CT

Chest scanogram of 23 year old male patient came with history of cough showing eliptical ares of increased opacity seen in the right upper lobe, medial end pointing towards the hilum and the lesion is sharply marginated.

Contrast enhanced CT scan showing non enhancing fluid attenuating lesion seen in the right upper lobe appears to be with in the dilated bronchi of posterior segment of right upper lobe. Can better appreciate on coronal reformatted image.

Bronchocele is commonly seen in congenital bronchial atresia, where there will be fluid accumulation in the bronchus distal to the atretic segment of bronchus. There are other rare causes for bronchocele like tumor obstructing the segmental bronchus, commonly carcinoids. The distal involved alveoli may show hypoplasia or a probable consequence of decreased ventilation and perfusion. These alveoli however remain open by collateral air drift occurring by the interalveolar pores of Kohn (air drift) or the bronchoalveolar channels of Lambert or the interbronchiolar channels with some amount of air trapping. Although radiograph is the first investigation to be done and suspected on it. The findings may show as described above in our case. Spiral CT is the examination of choice, not only to show all the components of the anomaly and to estimate the extent of air trapping but also for ruling out differential diagnosis such as bronchogenic cyst, bronchiectasis, aspergillosis, completely thrombosed arteriovenous malformation or pulmonary aneurysms and tumors.

Annular Pancreas - Barium meal.

34 year old male patient came with recurrent pancreatits. Barium meal showing smooth narrowing in the second part of duodenum. Annular pancreas was confirmed on MRCP.

Annular pancreas is a rare congenital anomaly in which incomplete rotation of the ventral anlage leads to a segment of the pancreas encircling the second part of the duodenum. It has a prevalence of one in 2,000 persons and occurs either as an isolated finding or with other congenital abnormalities. There are two types of annular pancreas: the extramural type and the intramural type. In the extramural type, the ventral pancreatic duct encircles the duodenum to join the MPD. In the intramural type, the pancreatic tissue is intermingled with muscle fibers in the duodenal wall, and small ducts drain directly into the duodenum.

Annular pancreas can be diagnosed on the basis of CT and MR imaging findings that reveal pancreatic tissue and an annular duct encircling the descending duodenum. ERCP is useful in substantiating the diagnosis and defming the ductal anatomy. ERCP shows a normally located main duct in the pancreatic body and tail and encirclement of the duodenum by a small duct in the pancreatic head. In most cases (85%), the duct within the annular portion of the pancreas communicates with the main pancreatic duct.

Primitive Neuroectodermal Tumor (PNET) of Skull vault : CT and MRI

4 year old female child came with history of mass in the right side of the head in parietal region. CT scan shows large heterogenously enhancing soft tissue mass lesion seen in both intra and extracranial regions, the intracranial component is extradural causing mass effect on the right cerebellar hemisphere. There is bone erosion of right parietal bone.

MRI of the same patient T2 WI showing similar findings with large extra and intracranial components. There is complete involvement of the right parietal bone. Biopsy proved to be PNET.

Primitive Neuroectodermal Tumor (PNET) is a soft tissue sarcoma classically described under small round blue cell tumors (SRBCT). Synonyms include : PNET, Peripheral neuroepithelioma, Peripheal neuroblastoma, Askin tumor (Thoracopulmonary PNET) and Extraosseous Ewing's sarcoma. The incidence is 1% of the sarcomas. They often (75%) occure in the age of less than 35 years. Most investigators now believe that Ewing's sarcoma and PNET are different morphological expressions of one tumor type. In general, Ewing's sarcoma arises within the bone while PNET arises within soft tissues. PNET arising from the dura or skull vault is very rare and in this case it is diffucult to predict the origin of the tumor.Radiograph is often the first investigation to be done. CT and MRI are the investigations of choice to see for the extent of the lesion. MRI is preferred over CT scan. These can be used to look for the response to chemo and radiotherapy.Here is the link to the PNET at various sites:

http://www.thedoctorsdoctor.com/diseases/pnet.htm

Pseudoachalasia of the cardia-Ba Swallow and CT

66 year old male patient presents with history of dysphagia for solids and liquids since 3 months and chest radiograph was normal. Barium esophagogram showing long segment smooth narrowing in the distal esophagus with significant dilatation and hold up of contrast in the proximal esophagus. On noticing carefully there is mild irregularities in the GE junction and cardiac end of stomach. We kept the possibility of achalasia and pseudoachalasia. Advised further workup of CT scan and endoscopy.

Contrast enhanced CT scan with on table oral contrast showing concenteric wall thicekning (arrow) obliterating the lumen in the distal esophagus involving GE junction and having less than 90 degrees of contact with the descending thoracic aorta and abutting left atrium. Endoscopic biopsy revealed adenocarcinoma. These findings are consistent with pseudoachalasia.

Achalasia cardia is due to loss of myenteric ganglion cells in the gastroesophageal junction and the etiology is idiopathic. But a similar clinical picture can be produced by other diseases, a condition termed as secondary or pseudoachalasia. A very high index of suspicion is required for the diagnosis of this condition because this is most commonly produced by a malignancy involving the gastroesophageal junction which is likely to be missed. In true or primary achalasia, there is loss of myenteric ganglion cells with loss of peristalsis in esophageal body and failure of lower esophageal sphincter to relax when swallowing. Barium swallow shows a typical bird's beak appearance.

The causes for pseudoachalasia include primary malignancy of esophagus or gastroesophageal junction, 53.9%, secondary malignancies such as metastasis from lung or breast, 14.9%, benign disorders like mesenchymal tumors, secondary amyloidosis and peripheral neuropathy, 12.6%, and as a postoperative complication following antireflux surgery, 11.9%. Other rare causes are neurological disorders like meningomyelocele, brain metastasis, infiltration by lymphoma and paraneoplastic syndromes associated with small cell carcinoma lung, bronchial carcinoids and pleural mesothelioma.

It is very important to differentiate pseudoachalasia from true achalasia. The patients with pseudoachalasia tend to be older in age ( more than 60 years), have shorter duration of dysphagia (less than 6 months) and have more substantial weight loss. Barium swallow may reveal a nodular of shouldered segment of distal esophageal narrowing. The length of the narrowed esophageal segment was found to be longer than 3.5 cm in 80% of the patients with pseudoachalsia which is the most important feature in radiological differentiation. A CT scan may show asymmetric thickening of the esophageal wall or cardia, mediastinal lymphadenopathy or may identify primary malignancy in secondary achalasia.

Methylmalonic acidaemia (MMA)

3 year old female child came with developmental delay, lethargy, seizures and hypoglycemia, MRI brain T2 weighted image at the level of basal ganglia showing bilateral symmetrical hyperintensities in globi pallidi.

MMA encompasses a heterogeneous group of disorders characterized by accumulation of methylmalonic acid and its by-products in biological fluids. These disorders are due to a deficiency of the adenosylcobalamin-dependent enzyme methylmalonyl-CoA mutase (apoenzyme deficiency), a defect in intracellular cobalamin metabolism (coenzyme deficiency), transcobalamin II deficiency, intrinsic factor deficiency, or dietary cobalamin deficiency, which is found in vegetarians. The incidence, as derived form a neonatal screening program, is one in 48,000 live births (6). The actual occurrence, however, is estimated to be one in 25,000 live births.

CT and MR imaging of the brain typically reveal atrophy, delay in myelination, and abnormalities in the basal ganglia, predominantly in the globi pallidi. The globi pallidi are particularly sensitive to mitochondrial dysfunction, and are thus prime targets for injury. MR Spectroscopy may show elevated lactate levels either in CSF or in brain parenchyma i.e regions of infarcts. Differential diagnosis for bilateral globi pallidi lesions are HIE (hypoxic ischemic encephalopathy), kernicterus, mitochondrial encephalopathy etc.

MOYAMOYA DISEASE

Two year old male boy presented with recurrent episodes of transient ischemic attacks since the age of 6 months following which he has delayed milestones. The boy also has seizures since one year. He was referred to MRI brain for further evaluation.

Figure a) T1weighted image at the level of basal ganglia show multiple tiny low intensity rounded areas seen in bilateral basal ganglia (arrows) which appear hyperintense on T2 weighted images suggestive of collateral vessels. c) Fluid attenuation inversion recovery (FLAIR) sequence showing atrophy involving bilateral frontal and left parietal cortical areas with chronic ischemic changes. d) Volume rendered 3D time of flight frontal projection cerebral angiography showing significant stenosis in the supraclinoid internal carotid arteries on both the sides with absent flow in the anterior and middle cerebral arteries and multiple collaterals in bilateral basal ganglia appearing as “puff of smoke” (moyamoya). Cause is unknown in this boy.

Discussion:

The term ‘moyamoya’ means ‘wavering puff of smoke’, described by Takaku, Suzuki and others in Japan in the sixties1. Moyamoya disease is a cerebrovascular disease that features narrowing or stenosis, starting at the distal internal carotid and proximal portions of the anterior and middle cerebral arteries of unknown etiology. Moyamoya syndrome is a phenomenon caused by an oligemic state similar in presentation but caused by various disease entities. Some of the conditions associated with Moyamoya syndrome are chromosomal disorders (Neurofibromatosis, Down’s syndrome), hemolytic anemias, infectious diseases (leptospirosis, tuberculous meningitis), neoplasms (Craniopharyngioma, Wilms tumor), drug abuse (phenobarbitol) and others. Etiology of Moyamoya disease is still unknown. There have been recent reports of increased familial incidence of the disease with markers on chromosome 6 and 17, located at 3p24.2-26 and a possible linkage of the marker D6S441 to the disease on chromosome 6. Moyamoya is commonly seen during first decade of life. Frequently the children present with transient ischemic attacks or ischemic strokes. Cerebral ischemia may also present as reversible ischemic neurological deficit, sensory attacks or acute infantile hemiplegia. Headaches, involuntary choreiform movements, seizures and other motor disturbances have been described2.

Majority of children (50-60%) show atrophy of anterior brain more than posterior brain on CT scan, where as adults show hemorrhage especially in intraventricular region. Contrast enhanced CT shows enhancing dots in basal ganglia and ‘net like’ vessels at the base of brain. MRI and MR angiography are diagnostic imaging modality of choice. MRI show multiple dot-like flow voids in basal ganglia on T1 weighted image (WI). Flow voids in the multiple collateral vessels in the cisterns appearing as ‘net like’ cisternal filling defects, associated with hyperintense small vessel cortical and white matter infarcts are seen on T2 WI. Slow flowing engorged pial vessels with thickened arachnoid membranes appear as bright sulci called leptomeningeal “ivy sign”. MR angiography show narrowed distal ICA and proximal Circle of Willis vessels with multiple lenticulostriate and thalamoperforator collaterals giving appearance of a “puff of smoke”. MR spectroscopy will show lactate peak in acutely infracted tissue. Treatment is mainly Encephalo-duro-arterio-synangiosis (EDAS) which is a method of indirect bypass2.

Teaching point:

Moyamoya disease or syndrome should be suspected in a child with recurrent ischemic attacks. MRI with MR angiography is the investigation of choice in this condition. MRI shows multiple dot-like flow voids in basal ganglia on T1 WI and flow voids in the multiple collateral vessels in the cisterns appear as ‘net like’ cisternal filing defects on T2WI. MR angiography show narrowed distal ICA and proximal Circle of Willis vessels with multiple lenticulostriate and thalamoperforator collaterals giving appearance of a “puff of smoke” which is typical appearance of moyamoya.

References:

1. Hoffman HJ. Moyamoya disease and syndrome. Clin Neurol Neurosurg1997; 99 Suppl 2 : S39-44
2. Gosalakkal JA. Moyamoya disease: a review. Neurol India. 2002 Mar;50(1):6-10.
3. Fujisawa I, Asato R, Nishimura K, Togashi K, Itoh K, Noma S, et al. Moyamoya disease: MR imaging. Radiology. 1987 Jul;164(1):103-5.