Medial Epicondyle Fracture of the Humerus

AP views of both elbows of an 18-year-old boy who sustained an injury to the right elbow.  There is an avulsion fracture (arrow) of the medial epicondyle of the right humerus. Radiograph of the left side demonstrates different areas of distal humeral structures from medial to lateral: medial epicondyle, trochlea, capitellum and lateral epicondyle. 

Facts:

• Common pediatric elbow fracture (3rd common, after supracondylar and lateral condylar fractures)
• Valgus strain at elbow joint
• Two main types: simple avulsion (1/2) and fracture-dislocation (occurring with lateral elbow dislocation; 1/2)
• Indications for surgery include 1) displaced fragment trapped in joint preventing reduction, 2) ulnar neuropathy, 3) valgus instability, 4) open fracture

Imaging:

• Look for displaced fragment trapped in the joint and degree of displacement because they might indicate surgery
• In patients less than 8 years, trochlea may be non-ossified and this may be confused with fracture of medial condyle, which is rarer and could be more complicated
• Another imaging Ddx is osteochondrosis

References:

Wilson JN. The treatment of fractures of the medial epicondyle of the humerus. J Bone J Surg 1960;42:778.

Gottschalk HP, Eisner E, Hosalkar HS. Medial epicondyle fracture sin the pediatric population. J Am Acad Orthop Surgeons 2012; 20:223.

Wheeless' Textbook of Orthopedics link

Mosaic Pattern of Lung Attenuation

Axial CT images of the chest in lung windows (inspiratory images) shows multilobular areas of variable lung attenuation (mosaic pattern) with dark areas showing diminished size/numbers of pulmonary vessels indicating that these dark areas are abnormal. 

Facts:

• Lobular or multilobular distribution of variable lung attenuation
• Three possible groups of etiologies: small-airway, vascular and infiltrative disease 
• Additional findings are helpful to distinguish the three causes

Making Decisions

1. Dark or white areas are abnormal? Looking at size and number of vessels in both regions. If they are similar, the "white" is abnormal (meaning it is ground glass abnormality). If the size/number of vessels in dark areas are decreased, this is either small-airway or vascular pathology
2. If the "white" is abnormal, look for differentials of ground glass opacity (GGO)
3. If the "dark" is abnormal, look at expiratory phase scanning. If air trapping is present, this is small-airway disease. If there is no air trapping, this is likely vascular cause
4. If expiratory scanning was not available, look at clinical features.  Dyspnea, cough, wheezing and response to bronchodilators are common in patients with small-airway disease and infrequent in vascular lung disease

Our case: We did not perform expiratory scan in this patient but given clinical scenario, the dark areas likely represent mosaic pattern from known chronic pulmonary embolism with pulmonary hypertension. 

Reference:

Stern EJ, et al. CT mosaic pattern of lung attenuation: distinguishing different causes. AJR 1995;165:813.

Pseudothickening of Colonic Wall

Axial and coronal-reformatted CT images of a 58-year-old woman show apparent circumferential wall thickening of the sigmoid colon (arrows) with a smooth transition into the more proximal colon. No pericolonic fat stranding is seen. Colonoscopy was performed but showed no colonic pathology.  Subsequent follow-up CT was also normal.  

Facts:

• When distended, normal colonic wall should be less than 3 mm or even imperceptible
• Fecal contents, fluid or colonic redundancy make true wall measurement difficult or impossible

Pseudothickening of Colonic Wall

• Could be mistaken for true pathology such as annular neoplasm or inflammatory stenosis
• Pseudothickening should be mild. Its margin should gradually return to full distention
• Normal pericolonic fat

References:

Mang T et al. Pitfalls in multi-detector row CT colonography: a systematic approach.. Radiographics 2007;27:431.

Macari M, Balthazar EJ. CT of bowel wall thickening significance and pitfalls of interpretation. AJR 2001;176:1105.

Olfactory Groove Meningioma

Axial T2W MR image shows a lobulated extraaxial mass in the midline anterior cranial fossa. The mass is T2 isointense with a central area of higher T2 signal intensity. Mild brain edema of the inferior frontal lobes are noted. 

Sagittal post-contrast T1W MR image shows uniform enhancement of the mass.  It better demonstrates the location of the mass that is anterior to the tuberculum sellae.

Facts: Olfactory Groove Meningioma

• Usually asymptomatic until large. 
• When symptomatic, they can produce Foster Kennedy syndrome (anosmia, ipsilateral optic atrophy, contralateral papilledema), metal status change, urinary incontinence
• Histological variables follow WHO grading I to III (from low recurrence to high rates of recurrence with aggressive growth)
• Atypical meningioma, rhabdoid and malignant meningioma have greater risk of recurrence
• Brain invasion increases likelihood of recurrence but not indicator of malignant grade
• "Olfactory groove" is anterior to tuberculum sellae (distinction between tuberculum vs olfactory groove meningioma). Tuberculum sellae is bony elevation between chiasmatic sulcus and sella turcica. See tuberculum sellae meningioma here (external site)

MRI Findings

• T1 and T2 isointensity
• Most enhances with gadolinium
• Dural tail
• Signal voids in the lesion due to calcifications

Reference:

Cranial Base Center of Massachusetts General Hospital website 

Lipoma of Filum Terminale

Sagittal T1W image shows a T1 hyperintense mass at the filum terminale and a thin fatty strand extending from the tip of the conus medullaris to the coccyx.

Sagittal T2W image with fat suppression demonstrates signal loss of the mass, indicating presence of fat.

Facts:

• Abnormal retrogressive differentiation of pleuripotential cells found in distal caudal mass
• Mostly incidental, found in 5% of lumbar spine MRI but may be associated with tight filum terminale syndrome
• Fat is clearly separable from nerve roots and conus medullaris that terminates at above L2 level

Imaging

• Fat intensity mass (hyperintense T1, hyperintense T2, and progressive lower signal on greater T2 weighting)
• Can be intradural or extradural
• Intradural fatty filum is fusiform, tapering down toward where the filum pierces the dura
• Extradural fatty filum is often larger, more diffuse, elevating/distorting distal thecal sac

Reference:

Atlas SW. Magnetic resonance imaging of the brain and spine, 4th edition, 2009