Madan Mohan Gupta, N.U.

 A 15- month-old male patient brought by his parents with complains of one episode of focal seizure involving right side of body, developmental delay and disproportional increase in size of head (left>right). Birth history was normal: full term, vaginal delivery and unremarkable. His laboratory investigations were within normal limits.

. T2W axial images showed disproportionate enlargement of left cerebral hemisphere with shallow sulci and enlarged gyri as compared to right side. There was enlarged lateral ventricle with colpocephaly with contralateral displacement of posterior falx and occipital lobe (arrow).

. T1W axial images showed disproportionate enlargement of left cerebral hemisphere with shallow sulci and enlarged gyri as compared to right side. There was enlarged lateral ventricle with colpocephaly with contralateral displacement of posterior falx and occipital lobe (arrow).

. FLAIR axial images showed disproportionate enlargement of left cerebral hemisphere with shallow sulci and enlarged gyri as compared to right side. There was enlarged lateral ventricle with colpocephaly with contralateral displacement of posterior falx and occipital lobe.

. Gradient echo (GRE) and diffusion weighted (DWI) axial images showed similar findings as mentioned previously on T2W, T1W and FLAIR images, and no evidence of abnormal signal intensity of calcification or hemorrhage in GRE and abnormal restricted diffusion in DWI.

. T2W sagittal images showed normally developed corpus callosum and brain stem.

MRI of the brain was performed using T2W, T1W, FLAIR sequences in 1.5 Tesla Siemens Magnetom Essenza.

On T2W, T1W and FLAIR weighted images: Disproportionate enlargement of left cerebral hemisphere with shallow sulci and enlarged gyri as compared to right side. There was enlarged lateral ventricle with colpocephaly with contralateral displacement of posterior falx and occipital lobe. However, there was no evidence of abnormal calcification or associated developmental venous anomalies.

: Hemimegalencephaly is a rare congenital disorder of cortical malformation with hamartomatous overgrowth on all or a part of a cerebral hemisphere. This results from either increased proliferation or decreased apoptosis (or both) of developing neurons. The majority (90 percent) of patients is presented with focal and generalized infantile spasms and developmental delay, hemiparesis and hemianopia are usually also evident.

Hemimegalencephaly is divided into three forms:

1. Isolated form
2. Syndromic form: associated with a variety of syndromes typically including hemicorporal hypertrophy of the ipsilateral part of the body. Such associated syndromes include:

• Epidermal nevus syndrome
• Klippel-Trenaunay syndrome
• McCune-Albright syndrome
• Proteus syndrome
• Unilateral hypomelanosis of Ito
• Neurofibromatosis type 1 (NF1): rare
• Tuberous sclerosis: rare

3. Total hemimegalencephaly: hemihypertrophy also involves the brainstem and cerebellum
All modalities able to image the brain (ultrasound, CT and MRI) will be able to more or less identify the key features, although MRI will give the best imaging. Typical MRI features of the affected hemisphere include:

1. Increased lateral ventricle size, sometimes may be small
2. Shallow sulci enlarged gyri
3. Enlarged/thickened calvaria 4. Contralateral displacement of the posterior falx
5. White matter calcification
6. Associated with developmental venous anomalies (DVAs)
7. The cortex of the involved hemisphere may be normal, but often demonstrates polymicrogyria/ lissencephaly/agyria /pachygyria and grey matter heterotopia

Differential diagnoses include:
• Enlarged hemisphere
• Gliomatosis cerebri
• Small hemisphere, making the normal hemisphere appear large
• Rasmussen encephalitis
• Dyke-Davidoff-Masson syndrome
• Sturge-Weber syndrome
• Other neuronal migration anomalies without overgrowth
• Polymicrogyria/ lissencephaly/agyria/pachygyria


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Articles

Case History: 15-month-old with focal seizure, developmental delay, disproportionate increase in size of head.

Hemimegencephaly

 A 65 year old patient presented with complaint of sudden onset of left sided hemiparesis. He also had complaints of a headache for the past five months. He has a known case of diabetes mellitus and IHD and has had regular treatment. Review of family history was unremarkable. On examination, there was severe loss of motor function on the left side of his body. The patient was then subjected to radiographic investigations.

. Non contrast CT brain shows a large well-defined broad dural based extra axial solid (arrow) cystic lesion in right parietal region causing buckling of underlying cortex and white matter oedema.

. Post-contrast CT brain shows a large well-defined broad dural based extra axial solid cystic lesion in right parietal region causing buckling of underlying cortex and white matter oedema with intense homogenous enhancement of solid portion of the lesion (arrow) and multiple intratumoral vascular channels (small arrow).

. Non-contrast MRI brain shows a large well-defined broad dural based extra axial solid cystic lesion in right parietal region causing buckling of underlying cortex (arrow) and white matter oedema with midline shift of 6 mm towards left side. The lesion appears hyperintense on T2WI with internal dural based solid portion and septations and hypointense on T1WI.

. Post-contrast MRI coronal T1 fat sat images intense homogenous enhancement of broad dural based solid portion of the lesion (arrow) and multiple intratumoral vascular channels (small arrow) and internal enhancing septae.

Non-contrast brain CT revealed a large well-defined broad dural based extra axial solid cystic lesion in right parietal region causing buckling of underlying cortex (Figure 1). On post-contrast study, solid portion of the lesion shows intense homogenous enhancement and multiple intratumoral vascular channels (Figure 2). Further brain MRI showed large extra axial broad dural based solid cystic mass in right parietal causing buckling of underlying cortex and white matter edema with midline shift of 6 mm towards left side (Figure 3).On post-contrast MRI, similar enhancement of the solid part was seen as on the CT and multiple intratumoral vessels and enhancing septae were seen (Figure 4).

 Cystic meningioma is applied to both meningiomas with intratumoral degenerative cyst formation as well as those with peritumoral arachnoid cysts or reactive intraparenchymal cysts. Patients present clinically in the same way as patients with non-cystic meningiomas, with symptoms related to increased intracranial pressure (ICP), focal neurology or seizures.

 divided cystic meningiomas into four subtypes according to the location of the cyst with respect to the brain and meningioma:
Type 1: Intratumoral cyst(s), located centrally within the meningioma
Type 2: Intratumoral cyst(s), located peripherally within the meningioma but still surrounded by tumor
Type 3: Cyst(s) located within the adjacent brain
Type 4: Cyst(s) located between the meningioma and brain (arachnoid cyst)

The tumor itself has imaging features identical to non-cystic meningiomas. The cysts are of variable size and can be entirely surrounded by tumor (types 1 or 2) or clearly between tumor and brain (type 4) or within the adjacent brain (type 3). On imaging it is sometimes difficult to distinguish between these types.

The differential is dependent on the location of the tumor. For tumors around the base of skull, cystic schwannoma (eg, acoustic schwannoma, trigeminal schwannoma) are the main differential, as they share the bright contrast enhancement, and are commonly cystic when large.


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Case History: A 65-year-old patient presented with complaint of sudden onset of left sided hemiparesis.

Cystic Meningioma

A 65-year-old woman presented with complaint of a dry cough, sore throat and mild fever. She was diagnosed with upper airway infection and she had experienced similar attacks in the previous three years.

. Chest X-Ray (PA and lateral views) shows large well-defined, well-marginated oval shaped homogenous opacity right mid zone which seems to be pleural-based and forming an obtuse angle with right lateral chest wall.

. Ultrasound with color Doppler shows a well-defined heterogeneous hypoechoic lesion with internal echogenic serpentine membranes and does not show internal vascularity.

. CECT scan shows well-defined thin-walled smooth marginated fluid density lesion in upper and middle lobe of right lung with few foci of air and calcification in its wall. The lesion shows internal hyperdense linear membranes. The lesion is forming an acute angle with the right lateral chest wall and does not show enhancement on post contrast study. There is no Mediastinal adenopathy, pleural effusion or other evidence of infection or malignancy within the lung. A well-defined smooth marginated non-enhancing cystic lesion with peripheral wall calcification and air foci in right lung with no Mediastinal adenopathy or pleural effusion is suggestive of hydatid cyst.

. Reformatted coronal CECT scan images show the above-metioned lesion is well-defined and forming an acute angle with the chest wall and lying in the upper and middle lobe of the right lung with air foci and calcification in its wall. No evidence of adjacent rib destruction and well-marginated non-enhancing fluid density lesion prove cystic lesion is benign.

. Lung window axial and reformatted saggital images show well-defined oval shaped opacity within the right lung with no adjacent consolidation, collapse or septal thickening.

Albendazole treatment was started and the patient is now doing well.

 Hydatid disease is a worldwide zoonosis produced by the larval stage of the Echinococcus tapeworm. The two main types of hydatid disease are caused by E. granulosus and E. multilocularis. The resulting large cysts in the lung are a special clinical entity called giant hydatid cysts. Small cysts are usually asymptomatic in hydatid disease. Coughing, chest pain and breathlessness are the common presenting symptoms. Diagnosis of an intact echinococcal cyst is usually based on a suspicion resulting from an unexpected finding on routine X-Rays. Radiographically, the cyst appears as a homogeneous spherical opacity with definite edges. CT scanning and ultrasound have added to the diagnosis of hydatid disease of the lung. Serological tests have limited diagnostic value. It is diagnosed by viewing the cystic membrane.

Hydatid cysts are typical, however, if the content is only partially evacuated, a waterline image appears, commonly referred to as the Camelot sign. Rupture of cysts may cause an anaphylactic reaction. When there is complete detachment of endocyst from the pericyst, it gives rise to the sign called “floating water lily.” A new sign called “congealed water lily” has been described, and is seen when the consistency of the fluid in the cyst changes from watery to viscid and the germinal layer within the viscid matrix gives rise to the appearance of curvilinear structure which no longer moves with the change of position of the patient. Progression from simple cyst to floating water lily cyst to congealed water lily cyst has been observed in many patients. “Hydatid sand” is seen in most of the scans which consist of leaked out scoleces, daughter cysts and calcareous corpuscles of Echinococcus tapeworms within primary or daughter hydatid cyst.


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Case History: 65-year-old woman with dry cough, sore throat and mild fever, had upper airway infection diagnosis and similar attacks in previous years.

Lung Hydatid Cyst

 A 26-year-old male presented with complaints of pain and swelling in his left knee joint. He had sustained a knee injury due to falling from a bicycle one month prior.

Upon ultrasound examination, there was a moderate amount of fluid with internal echoes noted in supra-patellar region which communicated with joint cavity. He was further evaluated by MRI of the left knee joint.

Upon MRI, there was moderate joint effusion, absent normal bow-tie sign in lateral meniscus and displaced torn flap of lateral meniscus, which was seen in intercondylar fossa, suggestive of bucket handle tear of lateral meniscus (double posterior cruciate ligament sign), and severely edematous and inflamed anterior cruciate ligament with grade III signal intensity in entire ligament with few fibers intact.

Figure 1. PD FAT SAT (PDFS) sagittal MRI, Figure 1a shows normal bow-tie sign (white arrow) in medial meniscus, and joint effusion. Figure 1b shows loss of continuity between the anterior and posterior horn of lateral meniscus, suggestive of absent bow-tie sign ( blue arrow) in lateral meniscus.

Figure 2. PDFS sagittal MRI shows a low intensity band parallel and antero-inferior to posterior cruciate ligament, which is the torn part of lateral meniscus giving rise to “double PCL sign.”

Figure 3. PDFS axial MRI, Figure 3a shows torn flap of lateral meniscus (white arrow) which is seen to be displaced in intercondylar fossa (blue arrow) in Figure 3b.

Figure 4. Sagittal MRI shows loss of continuity and hyperintense signal involving anterior cruciate ligament (arrow) suggestive of anterior cruciate ligament tear and preserved posterior cruciate and Humphrey’s ligament.

 Bucket handle tear of lateral meniscus, grade III anterior cruciate ligament tear, moderate joint effusion.

A bucket handle tear is a longitudinal tear of the medial or lateral knee meniscus that extends from the posterior horn toward the anterior horn. Bucket-handle tears are usually precipitated by trauma, and up to 40 percent are associated with an ACL injury. Lateral meniscus tears account for 10 percent to 40 percent of bucket handle tears. The radiographic diagnosis of a bucket handle tear is important because bucket handle tears comprise 10 percent of all meniscal tears and usually require arthroscopic or surgical repair to prevent degenerative change.

Two classic secondary MRI signs of a bucket handle tear are the double PCL sign and the absent bow-tie sign. The double PCL sign represents the posterior portion of the bucket handle, which is still attached to the main meniscal body but slides over the medial tibial eminence to lie in front of the PCL in the intercondylar notch. When the ACL is intact, this sign is specific for a medial meniscal tear, because the course of the ACL prevents lateral meniscus fragments from lying in the intercondylar notch. However, in a patient with a prior or simultaneous interruption of the ACL, a lateral bucket-handle tear can also produce the double PCL sign. Other low-signal structures that can be present in the intercondylar notch and must be differentiated from the double PCL sign include the ligament of Humphrey, a torn ACL, fracture fragments, osteophytes or loose bodies. In sagittal MRI of the knee, a bow-tie appearance is created by the anterior and posterior horns of the meniscus, which are seen as touching low-signal-intensity triangles. With 4- to 5-mm sagittal slices, a normal meniscus, which is 9- to 12-mm wide, should look like a bow-tie on at least two consecutive images. When a bucket handle tear forces the central portion of the meniscus into the intercondylar notch, the knot of the bow-tie disappears. Thus, the absent bow-tie sign, as defined by Helms et al, is the continuity of the anterior and posterior meniscal portions in none or only one sagittal image. The presence of this sign can also be due to congenitally hypoplastic or ring-shaped menisci, small menisci (in children and petite adults), partial meniscectomy or arthritic degeneration.


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Case History: 26-year-old male with complaints of pain and swelling in left knee joint, had sustained knee injury from falling from a bicycle one month prior.

Bucket Handle Tear of Lateral Meniscus 

 A 60-year-old female presents with the complaint of breathlessness during rest, which increases on supine position and in rainy weather, not associated with smoke and dust; cough with non-purulent non-blood stained whitish expectorant; and fever. She is a known case of bronchial asthma and hypothyroidism. Patient is a retired teacher by occupation. Sputum microscopy is negative for acid fast bacilli and other micro-organisms. Upon laboratory investigation, there is peripheral eosinophilia and positive IgM antibody for aspergillus fumigates.

. Chest X-Ray shows multiple fleeting radiopacities in right upper lobe and dense tube-like soft tissue opacity extends from hilum of right lung to outwards in right upper lobe giving finger in glove appearance.

. HRCT scan revealed extensive central cystic bronchiectasis filled with high density mucus material involving right upper lobe (finger in glove appearance; arrow) and postero-basal segment of bilateral lower lobes. Multiple tiny nodules in bilateral lung fields, predominantly in upper lobes, with few of them showing peripheral tree in bud appearance. No evidence of mediastinal lymphadenopathy and pleural effusion, findings are suggestive of allergic broncho-pulmonary aspergillosis.

. CT (mediastinal window) showed multiple tubular structures filled with high density mucus material involving right upper lobe (finger in glove appearance; arrow) and postero-basal segment of bilateral lower lobes. No evidence of mediastinal lymphadenopathy and pleural effusion.

 Allergic broncho-pulmonary aspergillosis (ABPA)

 Aspergillus species are ubiquitous spore-forming fungi present in the environment, the one most commonly affected by humans is Aspergillus fumigates. Clinical presentation occurs in various forms, from active infection in locally destructive disease, or in the most severe form, bronchial wall thickening central bronchiectasis, mucoid impaction, tubular branching pattern of mucoid impaction giving a finger in glove appearance and no pleural effusion or adenopathy, tree in bud abnormality, migratory fleeting opacities and pulmonary disseminated infection in immunocompromised patients. ABPA is a hypersensitive reaction to Aspergillus mycelia that colonize the bronchi. Asthma and cystic fibrosis are common illnesses associated with ABPA. The prevalence of ABPA is reported to be 1 percent to 2 percent in asthmatics, 7 percent to 14 percent in steroid-dependent asthmatics, and 2 percent to 15 percent in cystic fibrosis. The most common misdiagnosis is TB due to the striking radiological similarity between ABPA and TB, resulting in the patient being treated with anti-TB drugs for a long period of time. The myco-serological tests, peripheral eosinophilia and anti IgM antibody to fungal antigen and radiological investigations like chest X-Ray and CT scan are required.

The chest X-Ray showed dense tube-like soft tissue opacity extends from hilum of right lung to outwards in right upper lobe giving finger in glove appearance and further confirmation by HRCT scan which revealed extensive central cystic bronchiectasis filled with high density mucus material involving right upper lobe and postero-basal segment of bilateral lower lobes. Multiple tiny nodules in bilateral lung fields, predominantly in upper lobes, with few of them showing tree in bud appearance. No evidence of mediastinal lymphadenopathy and pleural effusion.


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