Diffuse Idiopathic Skeletal Hyperostosis (DISH)

 

DISH or Diffuse Idiopathic Skeletal Hyperostosis, aka Forestier disease, is a common disorder of unknown etiology, characterized by intermittent pain and stiffness in the involved spine segments. Spinal involvement of DISH characteristically produces flowing type ossifications in the anterolateral margins of the at least 4 contiguous vertebrae. This ossification can be of variable thickness, can measure up to 2cm. 

The above images shows prominent ossifications in relation to the anterior aspects of C3 to C7 levels, with C4 to C7 appearing continuous. This is also causing mass effect on the hypopharyngeal soft tissue / pharyngo-esophageal junction. 

The 'Light bulb sign' of liver hemangioma [MRI]

 Light bulb sign refers to the persistent T2 bright homogeneous signal intensity of a typical liver hemangioma, on increasing the TE  (T2 weightage) of the image. The bright signal is compared to that of a glowing light bulb. This may however also be seen in hypervascular metastases. 

MRI Liver of an young patient with multiple hemangiomas in both lobes. 

On increasing the TE, the signal intensity of hemangioma is well preserved, whereas the signals of other structures such as liver and spleen gets reduced.  

Hemangiomas are T2 homogenously hyperintense, with well defined margins with or without small lobulatations. They appear hypointense in T1WI, hyperintense in DWI. In post Gadolinium images they show peripheral nodular intense enhancement in the arterial phase, with gradual centripetal filling-in of the contrast. In the delayed hepatobiliary phase hemangiomas appear hypointense as they do not contain any hepatocytes. 

Isolated Area Postrema Syndrome (APS) presenting as intractable nausea and vomiting (NMOSD)

 Area Postrema (AP) is an emetic reflex center, one of the circum-ventricular organs that is outside the blood-brain barrier(BBB). It is located in the dorsal aspect of the medulla, at the caudal end of the fourth ventricle. AP along with Nucleus Tractus Solitarius (NTS) and dorsal motor nucleus of Vagus forms the dorsal vagal complex, where most of the vagal afferents terminate. AP by its location outside the BBB is exposed to the toxins in the blood. Activation of the AP brings nausea and vomiting, due to its projections into the NTS. 

AP through its hypothalamic,brainstem connections also regulate fluid balance, immunomodulation etc. It also chemo-sensitive neurons regulating hiccups. 

Neuro Myelitis Optic Spectrum of Disorders (NMOSD) are a group of autoimmune inflammatory demyelinating diseases of the CNS. Most of these show characteristic antibody to aquaporin-4 (AQP-4) water channel. 

 Attacks of intractable nausea, vomiting or hiccups (INVH) in the presence of a dorsal medullary lesion is called as the Area Postrema Syndrome (APS) and upto 30% of NMOSD patients will have APS during their disease course. 

NMOSD lesions in the Area Postrema shows loss of AQP-4 immunoreactivity and inflammation and characteristically lacks necrosis and demyelination which is seen in spinal cord and optic lesions, explaining reversibility of the symptoms. Patients have to tested for Serum and CSF AQP4-IgG antibodies. 

Isolated APS is easily mistaken clinically and is often attributed initially to other causes like gastritis including H.Pylori, GERD, Cholecystitis, Pancreatitis, food poisoning, gastroparesis etc. 

Immunotherapy usually results in rapid relief of symptoms usually within 2-3 days, responding to Methyl Prednisolone or Immunotherapy in most cases. Refractory cases may need drugs like Azathioprine, MMF, Rituximab.   

Below are the MRI images of a young female with intractable nausea and vomiting. 

T2 and T2 FLAIR hyperintensity noted in the region of the Area Postrema, called the Inverted-V sign.

Bilateral symmetrical normal optic nerves.

No restricted diffusion seen in the abnormal signal areas of Area Postrema.

Corresponding sagittal T2 FLAIR image showing the level of Area Postrema.
Abnormal signal intensity is also seen in the inferior colliculi of midbrain in the sagittal image. 

Diagram showing the location of AP, NTS in the dorsal medulla.

Hepatocellular Adenomas

Hepatic / Hepatocellular adenomas are uncommon benign tumor commonly seen in young to middle aged women, with history of oral contraceptive use. 

👉 Hepatic adenomatosis:  >10 adenomas. Adenomas in hepatic adenomatosis is not related to the hormonal or other risk factors. They tend to be multiple, progressive, symptomatic, more likely to lead to hepatic dysfunction and possible malignant transformation. 

HCAs are now classified based on the genetic and pathologic subtypes as :

1. Inflammatory hepatocellular adenoma.
2. Hepatocyte-nuclear-factor-1-alpha (HNF-1α-mutated) hepatocellular adenoma. 
3. β-catenin-mutated hepatocellular adenomas.
4. Unclassified subtype (includes HCAs without any genetic abnormalities).

Typical hepatic adenomas show moderate arterial phase enhancement with washout in portal venous and delayed, appears isointense to rest of liver. Chemical shift imaging can produce loss of signal of the adenoma in out of phase images due to the presence of fat within.


Name two hepatocyte specific contrast agents?

1. Gd-BOPTA / Gadobenate Dimeglumine
2. Gadoxetate Sodium.

What will happen in case of HCA with hepatocyte specific contrast agents?
Ans : Will appear darker than rest of liver, as the hepatocytes in HCA are non-functional.

Easy to remember Hepatic Adenoma better as ‘Hepatocyte’ Adenoma, as it lacks biliary epithelium, portal vein and even Kupffer cells.

Incidence Ratio in Female to Male is 9:1, Why 

Ans: OCP use. (Anabolic steroids also increase the risk, common with young men).

Surgery is recommended irrespective of size, why?

1. Risk of rupture and shock.
2. Transformation into HCC.

Below MRI images are of a 25yr old female patient who presented with pain related to cholecystolithiasis. Three incidental slightly echogenic lesions are seen in both lobes during USG, for which MRI was suggested.

T2 weighted images showing slightly T2 hyperintense lesion in the superior subcapular portion of the left lobe, lateral segment. 

Another similar signal intensity lesion in right lobe, segment VII/VIII

The main lesion showing the signal intensity loss in the Out-phase images, suggesting intralesional microscopic fat content. No restricted diffusion were seen in these lesions. 

Subtlest of three in the superior portion of segment VII of right lobe, again showing the loss of signal intensity. 

Increasing the TE of T2 WI reduces the signal intensity of the lesion in addition to that of rest of the structures. (c.f. hemangioma shows similar signal on increasing TE). See this article to see how a hemangioma looks like on increasing TE ('The Light Bulb Sign')

  Dynamic post contrast images shows prompt arterial phase enhancement of the lesion (yellow arrow), and appearing someehat isointense to rest of liver in the further images.

References:

1. Luigi Grazioli, Lucio Olivetti, Giancarlo Mazza, Maria Pia Bondioni, "MR Imaging of Hepatocellular Adenomas and Differential Diagnosis Dilemma", International Journal of 
   Hepatology, vol. 2013, Article ID 374170, 20 pages, 2013.
2. Hepatocellular Adenomas: Correlation of MR Imaging Findings with Pathologic Subtype Classification, Radiology.
3. Hepatic Adenomas: Imaging and Pathologic Findings. Luigi Grazioli, Michael P. Federle, Giuseppe Brancatelli, Tomoaki Ichikawa, Lucio Olivetti, Arye Blachar, Radiographics.

Persistent Trigeminal Artery (PTA), Tau sign

Persistent Primitive Trigeminal Artery is one of the persistent carotid-vertebro-basilar anastomoses. PTA arises from petrous-cavernous junction, runs posterolaterally along the trigeminal nerve, crosses over or through dorsum sella.  

Two types of PTA have been described. 

Saltzman Type I : PTA supplies the distal basilar artery. PComs are usually absent. The distal basilar artery is absent or hypoplastic. Distal vertebral arteries are also hypoplastic. 

Saltzman Type II : PTA supplies the Superior Cerebellar Arteries, with PCAs supplied by the PCom. 

TOF MRA images showed Saltzman type I PPTA, where the PTA is seen replacing the distal basilar artery. 

Sagittal MIP MRA image showing the distal basilar artery completely supplied by the PTA. 

The Tau sign, resembling a 'T' is classically described in the sagittal images. 

Eosinophilic Gastroenteritis

Case: 40Y Male patient presented with abdominal pain and diarrhoea. 

Plain CT image shows thickened appearing colon (orange arrows) with surrounding fat stranding. Thickening of anterior pararenal fascia is also seen bilaterally (blue arrows). 

Contrast CT images showed edematous thickening of the terminal ileum (not shown) and large bowel upto distal descending colon. Peri-colonic inflammatory fat stranding is noted. The SMA-SMV, IMA-IMV showed normal contrast opacification. 

Contrast CT images showing mild right pleural effusion (yellow arrow) and ascites (green arrows). 

Differential Leukocyte count revealed Eosinophil count of 18% initially and rose upto 68% within 3 days. Peripheral smear showed normocytic normochromic picture with marked eosinophilia. 

Colonic biopsy showed dense chronic inflammation with predominance of eosinophils - features compatible with Eosinophilic enterocolitis.

Patient was treated with Steroids and Azathioprine, improved and was asymptomatic with normalized lab parameters in the last visit.  

Eosinophilic gastroenteritis  is a rare inflammatory disorder of the gastrointestinal tract, characterized by focal or diffuse eosinophilic infiltration of the gastrointestinal tract. Clinical features and radiological findings are non-specific, so a high index of suspicion is needed, in cases of peripheral eosinophilia (seen in >60%). This usually presents with dyspepsia and diarrhoea. It may rarely cause GOO / SBO and pancreatitis. This disease was first described by Kaijser in 1937.

Although any age group can be affected, majority of patients are in the 3rd to 5th decades, with a slight male preponderance. Most patients have history of seasonal allergies, asthma, food sensitivity, eczema, elevated IgE levels. 

EG is a self-limiting disorder in most cases and usually responds well to steroids. 

Three types of EG have been mentioned, 

1. Mucosal EG (most common) : presents with fecal blood loss, anemia, weight loss due to malabsorption or protein losing enteropathy.
2. Muscularis EG : presents with obstruction (GOO/SBO).
3. Subserosal EG : manifests as eosinophilic ascites. 

Definitive diagnosis of EG requires bowel biopsy correlation demonstrating the eosinophil infiltration. In cases of the subserosal EG, high eosinophil count in a sterile ascitic fluid by paracentesis can also be demonstrated. 

Major DD would be a intestinal parasites, which necessitates stool examination to look for ova and parasites. 

Hypereosinophilic syndrome (HES) is an idiopathic condition associated with marked peripheral eosinophilia (>1500/uL for >6months) and gastroenteritis. Heart, lungs, brain and kidneys are also affected in HES. 

Imaging features are non-specific, can show edematous wall thickening. Ascites and pleural effusion can be seen. Esophagus, stomach, small bowel and also colon can be affected. 

References:

• A Review of Eosinophilic Gastroenteritis.
• Radiopaedia. 

Thanks to Dr. GP. 

Radiation enteritis

Below are the CT images of a 60y female patient, post surgery, post chemo-radiotherapy for Ca Rectum 3 months before the CT. 

CT images show 'long segment, contiguous, mild circumferential wall thickening of distal and terminal ileum, measuring length of ~30cm and maximum wall thickness of ~6mm. No peri-enteric fat stranding or lymph node enlargement seen'.  There were no sinuses or fistulae or any features of bowel stricture or obstruction.  

The blue arrows point to the thickened ileal loops. 

Radiation induced enteritis, especially of the small bowel is less often seen even though small bowel is very radiosensitive, because of its relatively increased mobility. Among small bowel the terminal ileum is the most sensitive, as it is more or less fixed. Fixation due to adhesions from a previous surgery or previous inflammation (including PID) can increase the risk of radiation induced bowel damage. Thin habitus, diabetes and hypertension can also influence the post radiation injury. 

Radiation doses >50Gy administered over 6 weeks can produce radiation induced bowel injury, which in 10% of cases might require surgical intervention. ~5-15% patients receiving >45Gy develop chronic radiation enteropathy.

The three stages of radiation enteritis are acute, subacute (2-12 months) and late phase. Acute phase is usually the mucosal inflammation, crypt abscesses, superficial ulcerations. Subacute phase, is a phase of regeneration, arteriolar sclerosis. Late phase is usually due to fibrosis. This phase can result in strictures, obstruction, fistula and sinus formation. 

👉  Point to remember : Keep in mind the differential of radiation induced bowel injury, in cases of bowel wall thickening. Especially in a post op patient, ask for history of radiotherapy.