Sclerotic Skeletal Secondaries

T1 and T2 hypointense multiple lesions are noted in the dorsolumbar and sacral vertebrae, in the above MR images. These lesions are  hyperintense in STIR images. T1 and T2 hypointense signal intensity is suspicious for sclerotic nature of the lesions. Mild expansion of L3 vertebral body is also noted. No associated paraspinal soft tissue components were seen. Contrast MRI taken showed moderate enhancement in all lesions (not shown). 

Few similar signal intensity lesions are also seen in C6, D1 and D6 vertebral bodies.

CT images are confirmatory. L3 vertebral body lesion is extending to involve both pedicles and extending further into the posterior elements.

The most common cause for sclerotic bone metastases are prostate carcinoma in males and breast carcinoma in females. Occasionally transitional cell carcinoma of urinary bladder, gastric carcinoma, colonic carcinoma, neuroblastoma, testicular carcinoma and lymphoma can produce sclerotic metastasis. Carcinoid tumor of lung also usually result in sclerotic metastatic lesions.

Reference:

Chapman, 6th edition. 

ACL and Lateral Meniscus old avulsion fractures without marrow edema

Clinical history: 40Y M patient with previous history of knee injury, now presenting with lateral joint pain, ROM restriction, locking and sounds. 

ACL tibial attachment appears avulsed and displaced postero-superiorly. No marrow edema seen in the tibial attachment site or in the fragment. Orange arrows point to the avulsed fragment from the tibial intercondylar region, which appears more rounded and corticated.

 

Attachment site of anterior root of lateral meniscus is seen avulsed from the tibia, and is seen displaced slightly laterally from the anterior intercondylar region. No marrow edema was seen. Meniscal avulsion to produce a bony detachment is unusual. The meniscus usually detaches from the cortical surface of bone and is then called as a 'floating meniscus'. (Differential consideration for this would be a meniscal ossicle. But this is commonly seen in posterior horn of medial meniscus and a donor site would not be present in the tibia).

 

Irregular near full thickness cartilage losses of the central portion of lateral tibio-femoral compartment is noted with subchondral marrow edema of both surfaces. Yellow arrow points to the cartilage loss, green arrow to the marrow edema. These in addition to the tiny tibio-femoral marginal osteophytes, favor the development of secondary osteoarthritis. Lateral meniscal extrusion is also noted in the coronal images. Blue arrow(s) shows absence of marrow edema in the tibial intercondylar region, indicating the avulsions are old ones. A small old Segond fracture is also seen in the lateral proximal tibia. 

Prominent horizontal tear (yellow arrow) of posterior horn of medial meniscus is noted extending into the tibial surface and the posterior free margin. A multiloculated cystic area (green arrows) is noted close to the posterior horn of medial meniscus, seen communicating with the tear (orange arrow), suggesting a parameniscal cyst.

A small T2 hypointense intra-articular loose body is noted posterior to the medial femoral condyle.

 T2 oblique sagittal images showing the bony avulsions, the meniscal tear and the parameniscal tear.

Epidermoid cyst of the Cerebello-Pontine Angle (CPA)

Intracranial epidermoid cysts are uncommon congenital slow growing lesions which becomes symptomatic due to the development of mass effect on adjacent structures in the 2nd - 4th decade of life. They are most commonly located in the cerebello-pontine angle in almost 50% of the cases. It is the third most common CP angle mass after acoustic schwannomas and meningiomas.

In MRI these lesions appears almost isointense to CSF but shows a characteristic restricted diffusion. These appear as lobulated lesions that typically insinuates between the adjacent structures and encases the cranial nerves and vessels. Calcification is seen in 10%-25% cases.

Another characteristic feature of epidermoid and MRI is partial suppression sometimes called the dirty appearance in T2 FLAIR images. In rare cases when they are T1 hyperintense they are called as white epidermoid.

The following images are of a 25 year old male patient.

CSF intensity appearance of the epidermoid cyst  is noted in the T1 and T2 weighted images, with a dirty appearance (partial suppression ) in the T2 FLAIR images. Lesion is predominantly located in right CP angle cistern, with extensions into the right cervico-medullary cistern, pre-pontine cistern, sellar-parasellar areas (details mentioned below). 

Mass effect on the right lateral aspect of pons, middle cerebellar peduncle is noted with  displacement to left. Partial effacement of the fourth ventricle is present. No hydrocephalus was seen.

In the SWI image above no blooming artifacts are seen within the lesion. DWI and ADC images show characteristic restricted diffusion, which helps to differentiate the lesion from an arachnoid cyst.

T1 sagittal and T2 coronal images show the mass effect of the lesion on the adjacent brainstem and the right middle cerebellar peduncle. The 3D T2 CISS images show characteristic lobulated appearance of the epidermoid cyst with insinuations in the CSF spaces and encasement of the cranial nerves and vessels.

Lesion shows no post-contrast enhancement.

The video above shows the right CP angle epidermoid cyst in much more detail in the 3D CISS images, which is helpful in determining the extent of the lesion. Diffusion weighted images also shows the extent of the lesion better than the conventional images due to the CSF intensity of the major portion of the lesion in rest of the sequences.

Significant mass effect and marked lateral displacement with stretching of right trigeminal nerve cisternal segment is noted. The lesion is encasing the right VII-VIII nerve complex, cisternal segment of right oculomotor nerve, and partly encasing the cisternal segment right trigeminal nerve. Lateral displacement of the right oculomotor nerve is also noted by the lesion. Superiorly the lesion is extending into the anterior aspect of midbrain, sellar and suprasellar region, partly encasing the right ICA bifurcation and the pituitary infundibulum. It is noted in contact with the right uncus and floor of third ventricle, tuber cinereum and mammillary body. Partial encasement of the basilar artery and its bifurcation is also present.

References:

https://radiopaedia.org/articles/intracranial-epidermoid-cyst
 

Extensor Carpi Ulnaris (ECU) tendinosis with interstitial tear

Extensor carpi ulnaris tendinosis is one of the common causes of ulnar sided wrist pain. Extensor carpi ulnaris passes through a fibro-osseous tunnel (the sixth extensor compartment), lying within a bony groove on the dorsal surface of ulna. ECU is maintained in this groove by the extensor retinaculum and the ECU subsheath. The ECU subsheath is not attached to the tendon.

The ECU originates from two heads, one from lateral epicondyle and other from the posterior middle third of ulna and distally it inserts into the posterior aspect of the base of fifth metacarpal.  

Racquet Sports and golf athletes are at an increased risk of ECU tendon pathology. In non-athletes rheumatoid arthritis is also to be excluded. The pathologies which can affect the ECU tendon includes tenosynovitis, tendinosis, tendon instability and rupture.

The PDFS axial and coronal image above shows mild thickening and intermediate signal intensity of the ECU tendon favoring tendinosis, with thickening and hyperintense signal intensity of the tendon sheath with associated mild soft tissue edema (suggesting tenosynovitis).

Serial axial sections of the wrist (clockwise) shows thickened ECU tendon with irregular shaped hyperintense intrinsic linear signal intensity favoring and interstitial tear.

No subluxation or dislocation of the ECU tendon is noted from the ulnar groove. The ECU subsheath and the extensor retinaculum appears intact. The orange thick arrow corresponds to the retinaculum and the thin green narrow corresponds to the ECU subsheath.

The above T2 axial image of the wrist is also showing the intact ECU subsheath (green narrow).

References: 

1. https://radiopaedia.org/articles/extensor-carpi-ulnaris-tendinopathy
2. https://radsource.us/extensor-carpi-ulnaris-subsheath-injury/

Dilated occipital emissary vein in Idiopathic Intracranial Hypertension

 25Y female who presented with complaints of chronic headache, on examination was found to have bilateral papilledema. An MRI with MR venogram was taken to look for features of Idiopathic Intracranial Hypertension. MRI findings were partial empty sella, with minimal increase in the retrobulbar optic nerve sheath CSF content (not shown). No vertical tortuosity of the optic nerves were seen in the MRI.  

MR Venogram showed mild distal transverse venous stenosis. A dilated occipital emissary vein was noted with diameter of the intraosseous component measuring 4.5 mm and the diameter of the proximal extracranial segment measuring 4.7 mm. Rest of the major intracranial venous sinuses appear normal.

Emissary veins of the skull base and posterior fossa direct the cerebral blood flow into the cervical outflow tracts. These include the condylar (anterior, posterior and lateral) emissary veins, mastoid emissary vein and the occipital emissary vein. The occipital emissary vein is seen near the midline of the squamous occipital bone and it connects the torcula or the distal superior sagittal sinus to suboccipital veins, which further drain into the vertebral venous plexus and / or the deep cervical vein. 

Enlarged occipital emissary veins have been described in craniosynostosis , increased ICT and in thrombosis of transverse sinus or sigmoid sinus. 

Idiopathic Intracranial Hypertension (Syn: Benign intracranial hypertension or pseudotumor cerebri syndrome (PTCS)) are characterized by findings of enlarged empty sella, papilledema, vertical tortuosity of optic nerves, dilated subarachnoid spaces around cranial nerves and dural venous sinus stenosis (usually bilateral distal transverse sinuses). The occipital emissary vein in patients with idiopathic intracranial hypertension may be dilated because it acts as a collateral venous channel and its dilatation is considered a possible marker for IIH.

Reference: Hedjoudje A, Piveteau A, Gonzalez-Campo C, Moghekar A, Gailloud P, San Millán D. The Occipital Emissary Vein: A Possible Marker for Pseudotumor Cerebri. AJNR Am J Neuroradiol. 2019 Jun;40(6):973-978. doi: 10.3174/ajnr.A6061.