Thursday, September 27, 2012

Gluteus Medius-The Neglected One-MRI

53 yr old  lady with chronic pain right hip region with no  trauma, shows  ill-defined ,irregular , edematous foci  in the  tendon insertion region of greater  tuberosity, with possible fatty degeneration of muscle belly and no avulsion fracture. Gluteus minimus also shows similar features suggesting strain of glutei possibly responsible.

Teaching points by Dr MGK Murthy.
  1. Gluteus medius originates from outer surface of ilium and gluteal aponeurosis and inserts on to oblique  ridge  on the  lateral surface  of greater trochanter. A bursa separates  the tendon from the surface of the trochanter, over which it glides  for various functions. When the leg is straight it  abducts , when the hip is flexed internally rotates, when the hip is extended externally rotates, all functions aided by minimus .
  2. Dysfunction  of medius is best identified by positive Trendelenburg  test. Common cause( up to 46% in some series) of chronic backache, buttock pain  radiating to thigh
  3. Muscle strain versus  tendinopathy versus  partial or complete tears  are a spectrum that needs to be analyzed on imaging. X- ray may play role in identifying the bony abnormalities including spurring and chips or calcifications. USG is helpful particularly  in cases of  bursal evaluation and  as  initial assessor  of the dysfunction. MRI is the gold standard for evaluating both medius and minimus , with regards to size of belly, musculotendinous junction, tendinous insertion, marrow abnormality of trochanter, soft tissue abnormality, associated findings in hip joint . 

Iliotibial Band Friction Syndrome-MRI

The iliotibial band  is a thick band of fascia formed proximally at the hip by the fascia of the gluteus maximus, gluteus medius and tensor fascia latae muscles. It inserts onto Gerdy's tubercle on the anterior lateral tibia and the intermuscular septum of the distal femur.When the knee flexes, the ITB moves posteriorly along the lateral femoral epicondyle. When the band is excessively tight or stressed, the ITB rubs against the epicondyle irritating the lateral synovial recess. 

Monday, September 24, 2012

Knee-Avascular Necrosis-MRI

This is a patient on long term steroids with knee pain. MRI Knee shows infarcts/AVN in femur and tibia along with marrow edema. There is focal serpiginous low signal line with fatty center, which is characteristic. 

For bone infarction or avascular necrosis, MRI is the most sensitive  modality and demonstrates changes well before and plain film changes are visible. The progression is:
  1. diffuse oedema
  2. focal serpiginous low signal line with fatty center (most common appearance)
  3. double line sign
  4. osteochondral fragmentation : rim sign
  5. secondary degenerative changes.

Wednesday, September 19, 2012

Aural Polyp- CT

20 yr old  male with clinically aural polyp , on  CT shows a  , large, expansile,  subtly destructive , Soft tissue density lesion with stippled areas of hyperdensity, involving External Auditory canal  with extension to middle ear and partial resorption of ossicles , suggesting, associated cholesteatoma along with aural polyp.

Teaching points by Dr MGK Murthy.

·         Benign soft issue tumors of EAC include  aural polyp, lipoma, hemangioma,  arteriovenous malformations,  lymphangioma, leiomyoma, myxoma and neural tumors like schwannoma, glandular  tumors like ceruminoma or pleomorphic adenoma. Aural polyps are  a result of chronic inflammation and elicit usually no bone resorption or destruction. Biopsy is mandatory as they can mimic squamous or basal cell carcinomas. High rate of underlying cholesteatoma(52%)
·         CT would help in assessing  the extent and surgical planning needed.    In children Suppurative otitis media  (SOM),broken tympanostomy tubes, Langerhans cell histiocytosis, and mycobacterial infection  could predispose to polyp formatio.  Treatment depends on underlying cause which needs therapy

Tuesday, September 18, 2012

Subacute Osteomyelitis-MRI

 70 yr old diabetic male  has pain in the left hip with fever of  recent onset with no history  of  significant trauma. MRI shows  a relatively well defined , irregular, predominantly fluid signal intensity lesion in the subtrochanteric region  , with  cortical break, soft tissue involvement,  no significant onion peeling or expansion  or endosteal  low signal margin. Though not classical, in the given circumstances,  subacute osteomyelitis of type 2  is possible.

Teaching points by Dr MGK Murthy

1.       Incidence is increasing  in view of liberal use  of antibiotics
3.       Roberts  radiological  classification (1982) is generally accepted . Type 1-metaphyseal (1a is  punched out and 1b is  with sclerotic  margin classical brodies abscess, maximum in incidence), Type2- metaphyseal cortex and appear similar  to osteosarcoma , Type3- diaphyseal, cortical and looks like osteoid  osteoma , Type4- diaphyseal and looks  like ewing’s with periosteal  response, Type 5-epiphyseal and look concentric lucency, Type6-vertebral body and looks destructive.
4.       All bones involved, with lower limbs, specifically tibia more involved than others
5.       If the lesion tethers from epiphysis to metaphysis across the growth plate  serpigenously, it is called “serpentine sign”. Smaller paravertebral abscess, early new bone formation with bony bridging differentiate from TB in spine.
6.       Xray and 3 phase bone scan may help, but CT would help  pick up eccentric nidus of sequestrum (vs central nidus of osteoid osteoma)  and CEMR is  ideal for  complete evaluation.
7.       Bx and curettage if diagnosis is  in doubt (in 1/3 case looks like malignancy), antibiotics in others and followed by surgery if needed are  recommended

Sunday, September 16, 2012

Accessory foot muscle-MRI

This is a 30 year old with swelling on the lateral aspect of foot with evidence of soft tissue lesion in relation to the lateral aspect of the talus which appears isointense to the muscles on T1 and T2 weighted images & appears elongated extending from the anterosuperior calcaneum to the base of the 5th metatarsal. These findings may possible indicate an accessory muscle. Appearance may correspond to accessory abductor muscle of the fifth toe (which has been occasionally described in literature). Clinical correlation was suggested.

Friday, September 14, 2012

Coronary Artery Calcium-Dual-Energy Coronary CT Angiography

Latest issue of Radiology Published online before print July 24, 2012, doi: 10.1148/radiol.12112455, September 2012 Radiology, 264, 700-707. Authors suggest that virtual non-contrast-enhanced (VNC) CT series derived from dual-energy CT studies may be a feasible substitute for dedicated CT calcium scoring studies.  Coronary artery calcium identification and quantification based on dual-energy coronary CT angiographic studies may obviate dedicated CT calcium scoring studies and decrease patient radiation exposure and cost, the researchers concluded.

Wednesday, September 12, 2012

Long head of Biceps Rupture-MRI

Old patient with shoulder pain, MRI shows  evidence of increased fluid in the glenohumeral joint. Altered signal intensity is noted in the long head of biceps along with fluid in the tendon sheath. Short head of biceps appears normal. These findings likely indicate partial tear of long head of biceps. Ruptures of the proximal biceps tendon make up 90-97% of all biceps ruptures and almost exclusively involve the long head. Age may vary considerably in patients with biceps rupture, but typically, the patient with a rupture caused by impingement or chronic inflammation is in the fourth, fifth, or sixth decade of life. Acute traumatic ruptures may occur in younger individuals or in anyone engaged in predisposing activities.

Monday, September 10, 2012

Sturge- weber -syndrome – CT

35 year male presented with h/o frequent fall , seizures & abnormal cognitive state. On CT, extensive gyral and subcortical calcification is seen at right cerebral  parenchyma along with right cerebral atrophy. There is a thickening of right calvarial thickening along with hyperpneumatisation of  right frontal sinus. Findings are s/o sturge- weber- syndrome. Case Submitted by:  Dr. Hema Chaudhary(Resident)  &  Dr Sangeeta  Aneja ( Professor & HOD), LLRM medical college , Meerut

Saturday, September 01, 2012

Excessive lateral pressure syndrome-MRI

32 year old male complaints of chronic pain following old injury. MRI shows femoropatellar incongruence with lateral positioning of the patella suggesting lateralization.This is refered to as excessive lateral pressure syndrome, better demonstrated in  various femoropatellar articulation X-rays.

Teaching points by Dr MGK Murthy :
Not an uncommon cause of chronic knee pain in young individuals. Could be detected incidentally or following trauma including post surgery for various bony injuries. Etiology could be tight lateral retinaculum / lax medial retinaculum.
The signal intensity could appear different on axial MR due to attenuation of the  medial retinaculum, their by making the lateral retinaculum look more black due  to compact type I collagen.Congenital cases could be represented by fascial bands.

Artery of Percheron Infarction-MRI

66 year old Known Hypertensive with Altered Sensorium shows symmetrical  bilateral posteromedial thalami and mid brain restricted diffusion foci with reduced ADC values.

Teaching Points by Dr MGK Murthy :

Thalami and mid brain are supplied by many perforating arteries  (both anterior and posterior circulation) in a complex manner. The anterior circulation supplies the anteroinferior aspects of thalami and mid brain. Posterior circulation supplies the medial aspects of thalami and mid brain via P1 and P2 segments of PCAs.

Artery of Percheron is a solitary arterial trunk that arises from one of the PCAs and supplies both paramedian thalami and rostral mid brain. Occlusion of this will lead to bilateral posteromedial thalamic and rostral mid brain infarctions. Differential Diagnosis should include top of the basilar artery syndrome,  which can be identified by the infarctions in the superior cerebellar arterial territories as well.

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