Radiology in Thai

Tc-99m MAG3 renal scan of a renal transplant recipient, day 1 after transplant with oliguria, shows delayed excretion of tracer from the transplant kidney. Images in vascular phase (not shown) are normal (normal perfusion and uptake).
Facts

• May occur immediately or after an initial short period of allograft function
• Related to both donor and recipient factors
• More common in cadaveric kidneys of older donors who sustained warm ischemia time or prolonged hypotensive periods
• Presented with oliguria or anuria early after transplant
• Diagnosis made by exclusion of other factors. Traditional signs (tubular casts, low urine osmolality) not reliable if patients with native partially functioning kidneys
• Treatment: supportive, return to dialysis if anuric (expected recovery of renal function usually within 3 weeks)

Renal Scan

• Normal perfusion, variable uptake but no (or delayed) excretion
• Serial scans helpful in determining viability of oliguric kidneys, predicting recovery or deterioration

Reference:

Resnick MI, Older RA. Diagnosis of Genitourinary Disease, 2nd edition, 1997

Axial CT image shows a large partially thrombosed aneurysm of the right renal artery, which is extraparenchymal. On other images, the aneurysm is saccular, and appears to arise from the segmental artery.
Facts:

• True aneurysms involve all layers of the artery and usually inherited. They can be fusiform or saccular, and are more commonly extraparenchymal in location. Example: fibromuscular dysplasia, Ehlers-Danlos
• False aneurysms involve only some layers of the artery, usually are acquired and saccular. Examples: trauma, iatrogenic, dissection, mycotic
• Intrarenal aneurysms are intraparenchymal, can be either true or false aneurysm. Examples: polyarteritis nodosa, tuberculosis, neurofibromatosis

Indications for Intervention

• Symptomatic: rupture, pain, ischemia, infarction, hypertension
• Diameter more than 2 cm, enlarging or dissection
• Female patient who is pregnant, or contemplating pregnancy

Our case: False aneurysm probably due to dissection, surgical removal was performed in this symptomatic patient
Reference:Lew WK, Weaver FA, Otero CA, et al. Renal artery aneurysm. E-medicine, updated September 17, 2008

Case Contributor: Gopalaratnam Balachandra, M.D.Editor: Rathachai Kaewlai, M.D.

Coronal T1W and T2W MR images of the brachial plexus show a fusiform-shaped mass (large arrows) along the course of the right cervical nerve root (small arrow). The mass demonstrates heterogeneous low T1 and high T2 signal intensity. It has smooth, well circumscribed borders.
Axial T1W post contrast MR image shows heterogeneous enhancement of the mass (arrows) with a central area of non-enhancement.
Facts: Primary Brachial Plexus Tumor

• Rare tumor, most commonly benign with good prognosis after surgical resection
• Clinical presentations: pain, paresthesia, palpable mass
• Common pathology: schwannoma, neurofibroma. Other possibilities: malignant peripheral nerve sheath tumor (MPNST), desmoid, ganglion, epidermoid

Imaging

• MRI is the study of choice to delineate the margins of tumor from surrounding tissues
• Characteristic feature on any imaging techniques is close relationship with the parent nerve, which helps to exclude other possibilities such as lymphadenopathy, vascular anomalies, etc.
• Low signal on T1, high signal on T2 and heterogeneous enhancement
• MRI cannot differentiate schwannoma from neurofibroma

This case - Schwannoma of the brachial plexus in a 32-year-old woman who presented with pain in the right arm and right neck mass.
References:

1. Binder DK, Smith JS, Barbaro NM. Primary brachial plexus tumors: imaging, surgical, and pathological findings in 25 patients. Neurosurg Focus 2004;16.

2. Rettenbacher T, Sogner P, Springer P, et al. Schwannoma of the brachial plexus: cross-sectional imaging diagnosis using CT, sonography, and MR imaging. Eur Radiol 2003;13:1872-1875.

About Case Contributor: Dr. Balachandra is the head of the Department of Radiology at Government General Hospital in Pondicherry, S. India.

Supine radiographic study of a 41-year-old woman shows a focally dilated loop of large bowel (star) in the right side of the abdomen. There is little gas in the more distal colon.Axial CT image shows a dilated right colon (star) with a transition point with a 'whirl-like' appearance (shown on contiguous images) in the mid abdomen (arrow). The rest of the colon is not dilated. Findings are most concerning for closed loop obstruction.
Facts: Closed Loop Obstruction of the Colon

• Colonic obstruction is rarely caused by postoperative adhesion (less than 1%). It is most commonly due to tumor
• CT should be the next imaging work-up to look for a mass. Contrast enema should be omitted due to the risk of perforation
• Closed loop obstruction of the colon usually is due to volvulus, which can be sigmoid (80%), cecal (15%) or involving the transverse colon (5%). Long mesocolon can predispose to malrotated cecum and result in a bascule or volvulus
• Signs of closed loop obstruction on imaging include focally dilated bowel loop with little gas distally and proximally, transition point with a whirl-like appearance at the mesenteric root, mesenteric haziness and free fluid

Our case: transverse colonic closed loop obstruction due to extralong colonic mesentery
Reference:Halpert RD. Gastrointestinal imaging case review series, 2nd ed, 2008.

Ultrasound image of the right ovary shows a well-circumscribed complex mass (arrows) with cystic and solid components (arrowheads) in a 66-year-old woman with abnormality seen on CT scan.
Facts: Complex Ovarian Mass

• Long list of potential causes, encompassing tumor (primary and neoplastic), inflammation and infection in a postmenopausal woman
• Potential tumors: serous and mucinous cystadenoma/cystadenocarcinoma, teratoma, clear cell carcinoma, endometrioid carcinoma, necrotic primary or metastatic tumors
• Most of these (if we think it is neoplasm) would need to be diagnosed histologically because imaging findings are nonspecific and malignancy cannot be excluded

Facts: Brenner Tumor

• Uncommon ovarian neoplasm, usually incidentally found
• Women in 5th to 7th decade of life
• Predominantly solid, but can be complex with cystic components when associated with serous and mucinous cystadenomas (seen in up to 30% of cases)
• Can be benign, borderline or malignant

Our case: Brenner tumor with struma ovarii on histology.
Reference:

Green GE, Mortele KJ, Glickman JN, Benson CB. Brenner tumors of the ovary sonographic and computed tomographic imaging features. J Ultrasound Med 2006;25:1245-1251.

PA and lateral chest radiographs demonstrate anatomic position of three heart valves, A = aortic, M = mitral and T = tricuspid, in a patient with rheumatic valve disease. Note that the tricuspid prosthesis is an annuloplasty.
Facts

• The three heart valves (aortic, mitral and tricuspid) commonly overlap each other on frontal radiograph. Correct radiographic identification can be difficult.
• To differentiate the mitral from aortic valve on lateral view, one draws a line from the junction of the sternum and diaphragm to the carina. This line normally intersects aortic valve*. The valve below the line is mitral valve. The tricuspid valve is the one to the mitral valve.
• Without a lateral view, the best criterion for use in differentiating between aortic and mitral prostheses is the direction of flow (discernable in Starr-Edwards and most Bjork-Shiley prostheses). Orifice (en face or in profile) and orientation (vertical or horizontal) of prosthesis are less reliable.

* This may not always be true in patients who have deformed anterior chest wall or markedly enlarged right ventricle.
Our patient's mitral and aortic prostheses are disc type, so their direction of flow was not discernable.
Reference:1. Gross BH, Shirazi KK, Slater AD. Differentiation of aortic and mitral valve prostheses based on postoperative frontal chest radiographs. Radiology 1983;149:389-391.2. Miller SW, Boxt LM, Abbara S. Cardiac Imaging the Requisites, 3rd edition, 2009.

Author: Santip Srisuwan, M.D.
Fig. 1: Chest radiograph of an asymptomatic young woman shows small right lung volume with cardiomediastinal shift toward the right side, small right hilum and a characteristic scimitar-shaped structure in the right lower lobe (arrow).

Figs 2&3: Contrast-enhanced CT images (maximal intensity projection, and 3D volumetric images) show an anomalous right lower lobe pulmonary vein (arrows) descending vertically, draining the right lower lobe and entering the IVC.
Facts: Scimitar Syndrome

• Also known as venolobar syndrome, hypogenetic lung syndrome
• Associations: congenital heart disease 25% (usually atrial septal defect)
• Symptoms: usually asymptomatic. Patients may have dyspnea if there is a large left to right shunt

Imaging Findings

• Small right lung
• Diminutive right hilum
• Dextroposition of the heart
• Characteristic scimitar vein draining below the diaphragm

Reference:Hansell DM, et al. Imaging of diseases of the chest. Elsevier Mosby, 4th edition, 2005.
About Guest Author: Dr. Santip Srisuwan is a radiologist at Samitivej Hospital, Bangkok, Thailand.

Frontal radiograph of the lumbar spine shows fusion of the sacroiliac joints (arrowheads) and thin syndesmophytes along the lateral borders of the lumbar spine.
Facts: AS

• Prototype of seronegative spondyloarthropathies (SNSA), which is a group of disorders of chronic inflammation of sacroiliac joints and spine
• Frequency: about 0.1% - 6% across different population (most likely toward the lower end)
• Genetic risk factor = human leukocyte antigen (HLA)-B27
• Principal bone/joint abnormalities = sacroilitis, synovitis and enthesitis

Imaging Findings

• Imaging findings are incorporated into the modified New York criteria for ankylosing spondylitis, as one of the four criteria.
• Sacroilitis: pseudowidening, sclerosis, erosions and later ankylosis
• Grading of sacroilitis on radiographs can be viewed here (link to Google Document provided by Schering-Plough Ply)

Modified New York Criteria for ASDefinite AS if 4a or 4b AND any clinical criteria (1-3)1. Low back pain for at least 3 months' duration improved by exercise and not relieved by rest2. Limitation of lumbar spine motion in sagittal and frontal planes3. Chest expansion decreased relative to normal values for age and sex4a. Unilateral sacroilitis grade 3-44b. Bilateral sacroilitis grade 2-4
ReferenceKippel JH. Primer on the rheumatic diseases, 13rd ed, 2008.

Axial CT image shows a multilocular low density collection (arrow) beneath the enlarged right tonsil (arrowhead), which is displaced medially.
Facts: Peritonsillar Infection

• Peritonsillar space is a space between anterior and posterior tonsillar pillar, deep to the tonsillar capsule and below the superior pharyngeal constrictor muscle
• Infection of this space usually arises from tonsillitis or pharyngitis, which can lead to peritonsillar cellulitis or abscess

Differentiation between Cellulitis and Abscess

• Differentiation of cellulitis from abscess has a clinical value, since cellulitis is treated medically but abscess usually requires surgical drainage
• Clinical distinction of the two can be difficult; imaging such as contrast-enhanced CT or ultrasound have been utilized for this purpose
• On CT, abscess appears as a cystic/multilocular low density collection with enhancing rim, with or without presence of gas at the center. Cellulitis appears as homogeneous soft tissue swelling with obliteration of fat planes.

References1. Domino FJ. the 5-minute clinical consult 2007, 2007.2. Sakaguchi M, Sato S, Asawa S, Taguchi K. Computed tomographic findings in peritonsillar abscess and cellulitis. J Laryngol Otol 1995;109:449-451.

Figure 1: Axial unenhanced CT image of the brain shows an isodense mass in the left posterior fossa with minimal, if any, mass effect.
Figure 2: Axial contrast-enhanced T1W MR image shows a large homogeneously enhancing extra-axial mass (star) near the left petrous bone overlying the sigmoid venous sinus (arrow).
Facts: Meningioma

• Tumors of meningeal cells (typically arising from meninges but can also be found in the choroid plexus, tela choroidea and arachnoid villi); therefore meningiomas can be seen in the meninges, spinal canal, intraventricular, and pineal regions
• Common, greater than 20% of all primary intracranial neoplasms
• Female:male = 3:2 to 2:1; mostly in late middle age
• Pathology: benign, atypical and malignant

Imaging Features

• Homogeneous, lobulated, well-circumscribed mass with uniform dense enhancement following contrast administration
• Common locations: parasagittal > convexity > sphenoid ridge
• High attenuation on unenhanced CT, iso- to mildly hypointense on T1W MR images
• May calcify in up to 1/4 of all cases, best seen on CT. Calcifications can be microscopic, punctate, large, peripheral or central. Malignant meningiomas rarely calcify.
• Hyperostosis can be seen in up to 1/2 of cases that meningiomas are immediately adjacent to the bone. Common in 'en plaque' meningioma
• Uncommon to have bone destruction (if pure destruction think of metastasis, sarcoma or myeloma)

Our case: benign meningioma overlying the sigmoid sinus without invasion. It is important to note if the meningioma is adjacent vascular structures for optimal surgical planning.
References:1. Drevelegas A. Imaging of brain tumors with histological correlation, 2002.2. DeAngelis LM, Gutin PH, Leibel SA. Intracranial tumors: diagnosis and treatment, 2002.

Lateral view of the knee radiograph shows focal cortical irregularity and thickening at the posterior aspect of the medial condyle of the femur (arrow), consistent with a cortical desmoid. The arrowhead points to a fabella.
Facts: Cortical Desmoid

• Considered to be an avulsion of the medial supracondylar ridge of the distal femur
• Occurs only on the posteromedial epicondyle of the femur (insertion of adductor magnus aponeurosis)
• Common in older children
• Patients may complain of pain, or being asymptomatic (incidentally detected on radiograph done for other reasons)
• They may or may not show periosteal reaction; 1-3 cm in size, mixed sclerosis and lucency in the cortex

Reference:Helms CA. Fundamentals of skeletal radiology, 3rd edition, 2005.

A coronal-reformatted CT image (without IV contrast) shows an obstructing right ureterovesical junction (UVJ) stone (arrow), causing hydroureteronephrosis. There is enlargement of the right kidney with perinephric stranding (arrowheads) as a result.
Facts:

• Urolithiasis incidence in the U.S. and Europe approximately 0.1% - 0.4% of population
• Male to female ratio = 3:1
• Peak age during third to fifth decade of life
• Recurrence rate about 75% during 20 years

Detection Rates by Various Imaging Methods

• Conventional radiography 50-70%
• Intravenous urography (IVU) 70-90%
• Ultrasound 50-60%
• Normal-dose CT: sensitivity 94-100%, specificity 97%
• Low-dose CT: sensitivity 95%, specificity 95%

Advantages of CT over IVU

• Shorter examination time
• Avoid cost and complications of IV contrast
• Greater sensitivity for stone detection
• Higher potential for detection of abnormalities unrelated to stone disease
• Study directly compared low-dose (<>
• Meta-analysis of 7 studies of low-dose CT in 1061 patients showing 95% sensitivity and specificity for stone diagnosis

References1. Liu W, Esler SJ, Kenny BJ, et al. Low-dose nonenhanced helical CT of renal colic: assessment of ureteric stone detection and measurement of effective dose equivalent. Radiology 2000;215:51-54.2. Niemann T, Kollmann T, Bongartz G. Diagnostic performance of low-dose CT for the detection of urolithiasis: a meta-analysis. AJR 2008;191:396-401.

Figure 1: Frontal radiograph of the right wrist shows no apparent fracture. In retrospect, there may be slight indistinctness of the "eye" of the hamate hook.
Figure 2: Axial CT image at the level of the hamate shows a nondisplace fracture near the base of the hamate hook (arrow).
Facts:

• Uncommon fracture that is easily missed on radiography
• Hook of hamate fracture is more common than fracture of the hamate body
• Direct blow to the hook, or avulsion of transverse carpal ligament and pisohamate ligament
• Presenting with pain on ulnar side of the palm aggravated by grasp, point tenderness over the hook at 1 cm distal and radial to the pisiform
• Best seen on carpal tunnel view (radiography) or CT
• If displaced and untreated, avascular necrosis and nonunion may occur.

Imaging Features

• On frontal radiograph, there is absence or indistinctness of the "eye" of hamate (oval, dense cortical ring shadow over the hamate)
• On CT scan, the fracture line is apparent at the hook best seen on axial images. It can involve the tip or the base of the hook

Reference:Singh AK, Kaewlai R. Extremity Trauma. In: Soto and Lucey's Emergency Radiology the Requisites, 2008.

Axial CT image shows a 5-cm heterogeneous left adrenal mass (arrows) with ill-defined border anterolaterally, and a liver mass (arrowhead).
Facts: Adrenal Cortical Carcinoma (ACC)

• Rare tumor, 0.5 to 2 cases per million population
• Bimodal age peak - young children, and adults in 4th to 5th decades
• Male = female
• Tumor arises from adrenal cortex; 50% produces hormones (cortisol, androgens)
• Most common site of metastasis: liver and lung

Adrenal Masses: Size Matters

• Mass less than 2 cm: incidence of malignancy 1%
• 2-4 cm: 3% - 8%
• 4-6 cm: 8% - 25%
• Greater than 6 cm: 40% - 80%

Imaging Features

• CT or MRI can suggest the diagnosis if there is malignant feature: venous invasion and/or capsular invasion, metastasis to lymph nodes or other organs.
• Mass usually is large, 70% of ACC are larger than 6 cm on imaging
• Usually heterogeneous after contrast administration
• 30% are calcified (usually central)
• Enlarged lymph nodes seen in 1/3 of cases (usually at high para-aortic or paracaval)
• MRI may be used as an adjunct to CT for delineation of IVC invasion and extension

Our case: adrenal cortical carcinoma
References:1. DeVita VT, et al. DeVita, Hellman, and Rosenberg's Cancer: Principles & Practice of Oncology, 8th edition, 2008

2. Husband JE, Reznek RH. Imaging in Oncology, Volume 1, 2nd edition, 2004.

A scout CT image shows a linear gas in the right upper quadrant running in an inferolateral to superomedial orientation (arrows). There is gas in the left colonic wall (arrowheads).
Facts: Pneumoperitoneum on Upright Radiograph

• As little as 1mm of free gas can be detected on radiography in an upright position with a horizontal x-ray beam
• If the patient cannot stay upright, a lateral decubitus (preferably patient on the left side) can be performed. Free gas will collect between lateral liver margin and abdominal wall
• Best chance of detection of free gas is when the radiograph is taken after the patient remains in an upright (or lateral decubitus) position for 10 minutes

Facts: Pneumoperitoneum on Supine Radiograph

• More difficult to detect
• Large free gas can be seen indirect as gas collect in different locations
• Right upper quadrant features include 1) linear gas collection running in an inferolateral to superomedial orientation (representing gas in subhepatic space, as in our patient), 2) triangular gas collection right to the spine above the kidney shadow (gas in most posterior recess of the Morrison pouch)
• Visualization of the outer wall of intestine (Rigler's sign)
• Visualization of the falciform ligament of the liver

Our case: pneumoperitoneum due to perforated ischemic colitis.
Reference:

1. Eisenberg RL. Gastrointestinal Radiology: a Pattern Approach, 4th edition, 2003.

2. Menuck L, Siemers. Pneumoperitoneum: importance of right upper quadrant features. AJR 1976;127:753-756.

A frontal chest radiograph shows double density to the right of the spine (short arrows) and convex border of the left atrial appendage (long arrows).A lateral view of the chest shows posterior displacement of the left mainstem bronchus by an enlarged left atrium (arrowheads).
Signs of Left Atrial Enlargement (LAE) on Chest Radiography

• Convex left atrial appendage
• Double density on the right side of the spine (one of the earliest signs)
• Double density on the left side as the left atrium extends into the left lower lobe
• Posterior displacement of the left mainstem bronchus posteriorly on lateral view, and superiorly on frontal view
• Spreading of the carina

Common Causes of LAE

• Acquired: mitral valve disease (stenosis or regurgitation), left ventricular failure, left atrial myxoma
• Congenital: VSD, PDA, hypoplastic left heart complex

Our case: severe mitral regurgitation
Reference: Miller SW, Boxt LM, Abbara S. Cardiac Imaging the Requisites, 2009, 3rd edition.

Supine chest radiograph in an ICU patient shows the tip of an NG tube in the right lower lobe bronchus (arrow). New opacities are seen in the vicinity of the tip of the NG tube, which may represent hemorrhage or aspiration.
Facts:

• Incidence in ICU patients between 0.5% - 1.5% of all NG tube placement
• Right side more common than left, lower lobe more than intermediate bronchus or main bronchus
• In one study of 14 malpositions, nearly half of the cases had subsequent pneumothorax requiring chest tubes, and the other half experienced pneumonias at the same site
• Traditional criteria for determining proper positioning of an NG tube (i.e., sound heard over the stomach upon insufflation of air, aspiration of fluid, absence of coughing) may not work well in ICU patients who are usually obtunded, intubated, have impaired gag reflex, decreased laryngeal sensitivity and are on neuromuscular blocking agents.
• Routine radiography after placement of an NG tube in ICU patients can be helpful for detection of tube malposition
• Once detected intrabronchial NG tube malposition, one should look for evidence of pneumothorax. If not seen, a close follow up radiograph is recommended since delayed pneumothorax may occur.

Reference:

Bankier AA, Wiesmayr MN, Henk C, et al. Radiographic detection of intrabronchial malpositions of nasogastric tubes and subsequent complications in intensive care unit patients. Intens Care Medicine 1997;23:406-410.

Please click on images to view a larger versionRoutine swimmer's view (left images) shows slight anterolisthesis of C7 on T1, in a trauma patient who sustained neck injury but normal CT scan. A repeat swimmer's view focusing at the lower cervical spine was performed and show normal alignment.
Swimmer's View Lateral Cervical Radiograph

• Usually required to visualize C7-T1 junction. In one study, only 20% of cases receiving five-view cervical radiography (AP, lateral, bilateral obliques and odontoid) C7-T1 can be adequately seen.
• Downsides of this view are: high dose, high scatter, difficult positioning, usually not adequate on large patients or patients with shoulder injuries
• To visualize C7-T1 junction, one should avoid arm pulling in patients who sustained a cervical spine injury

Current Practice

• Now, most places replace cervical spine radiography with CT scan because of higher sensitivity for fracture, shorter scan time, and probably less costly (if combined the use of overall resources)
• Some institutions still perform an out-of-collar lateral radiograph after a negative CT scan to ensure no significant change in alignment that may occur in patients with isolated ligamentous injury not shown on CT. This exam usually includes lateral and swimmer's radiographs.

This case show a subtle malalignment seen on routine C7-T1 junction on a routine swimmer's view. This was cleared by repeating the study with a focus at lower cervical spine. Abnormality on the first image is believed to be due to different centering of x-ray beam and superimposition of structures.
Reference:1. Daffner RH. Cervical radiography for trauma patients a time-effective technique? AJR 2000;175:1309-1311.2. www.Wikiradiography.com

Axial CT images of the sinuses show complete opacification of the maxillary, ethmoid and sphenoid sinuses with widening of the sinus ostia (yellow stars) and opacity in the nasal passages (blue stars) in this patient with history of allergic rhinitis.
Facts: Sinonasal Polyposis

• Common finding in patients with chronic rhinosinusitis (2% - 16% of cases)
• Soft, yellow-white nasal polyps that consist of edematous stroma with eosinophilic infiltrates, covered by respiratory epithelium
• Predisposing factors: asthma, fungal sinusitis, Kartagener syndrome, ASA syndrome, cystic fibrosis
• Can be seen in healthy individual with no predisposition to polyps
• Usually multiple, bilateral polyps. Majority of polyps arise from uncinate-turbinate-infundibulum space and bulla-hiatus seminularis-infundibulum
• On CT, there is opacification of the sinuses with widening of the sinus ostium and sinonasal passages

References1. Maroldi R, Nicolai P, Antonelli AR. Imaging in Treatment Planning for Sinonasal Diseases, 2005.2. Yousem DM, Da Motta AC. Head and Neck Imaging Case Review Series, 2nd ed, 2006.

Axial CT images show "railroad track" calcifications (arrows) in the left occipital cortex with ipsilateral enlargement of the choroid plexus (arrowhead) in this patient with a port-wine stain in the left V1 distribution.
Facts

• Also known as encephalotrigeminal angiomatosis
• Sporadic disorder affecting skin and central nervous system
• Defined as capillary malformation of the leptomeninges with or without choroid and facial V1 or V1-V2 involvement (port-wine stain)
• Probably due to embryonic defect of persistent vascular plexus in the neural tube during 6th week of embryonic development
• Port-wine stains can be unilateral or bilateral, most commonly involve V1 distribution but can also be extracranial
• Intracranial involvement always ipsilateral to the port-wine stain of the face, occipital lobe most common

Imaging

• MRI more sensitive than CT in identifying secondary changes due to leptomeningeal capillary malformation
• Cerebral cortical atrophy, compensatory ventricular and choroid plexus enlargement, calvarial hemihypertrophy and superficial gyriform enhancement after gadolinium injection
• "Railroad track" calcification of the cerebral cortex caused by precipitation of calcium likely due to alternation of vascular dynamics of the leptomeningeal malformation

Reference:Gorlin RJ, Cohen MM, Hennekam RCM. Syndromes of the Head and Neck, 4th ed, 2001.Muller-Forell WS. Imaging of Orbital and Visual Pathway Pathology, 2005.