Periorbital epidermoid cyst

Findings

Small hypodense lesion is noted along the right superolateral orbital rim (Hounsfield units approximately -6), causing smooth contoured external depression of the adjacent bone. No evidence of bone destruction or abnormal periosteal reaction. The globe, extraocular muscles, and orbital soft tissues appear normal.

Differential diagnosis:
- Epidermoid cyst
- Dermoid cyst
- Subperisosteal abscess
- Eosinophilic granuloma
- Metastasis (e.g., neuroblastoma).


Diagnosis: Periorbital epidermoid cyst


Key points

Dermoid and epidermoid cysts are found in a variety of locations around the skull and midface, typically classified as true choristomas. Choristomas are tumors that are composed of tissues not normally found at their site of occurrence, instead arising from the sequestration of surface ectoderm by closure of the underlying suture lines, neural tube closure, and diverticulation of the cerebral hemispheres. Dermoid cysts contain ectoderm and skin elements, whereas epidermoid cysts contain ectoderm but no skin elements. Histologic examination is necessary to differentiate the dermoid cyst with its squamous epithelium lining containing dermal appendages from the epidermoid cyst, which has no dermal appendages. Dermoid and epidermoid cysts are most commonly seen in midline and frontotemporal locations, followed by parietal locations. Midline locations include the anterior fontanel, glabella, nasion, vertex, and subocciput. Nasal dermal sinuses and dermoid and epidermoid cysts occur at multiple locations and may be associated with external skin ostia or deep sinus tracts, which may potentially extend intracranially.
Complete surgical excision of the dermoid or epidermoid is the recommended management, as the contents of the cystic lesion are irritating and may result in lipogranulomatous inflammation if ruptured. Deep orbital cysts extending into the orbital roof, temporal fossa, or intracranially may require neurosurgical assistance for removal.


Radiology

Careful investigation is important to distinguish deep from superficial lesions. CT attenuation will vary depending on cyst content. Similarly, the signal intensity at MR imaging depends on the contents of the cyst and may range from pure fluid signal intensity in an epidermoid cyst to a more complex signal intensity in a dermoid cyst. Epidermoid cysts also typically have bright signal intensity on isotropic diffusion-weighted MR images. With nasal dermoid cysts, high-resolution surface coil MR imaging is useful in determining if there is a connecting sinus tract in the prenasal space to the foramen cecum.

Phthisis Bulbi secondary to endophthalmitis from Serratia meningitis

Findings

Figure 1: Axial CT with contrast in this infant with meningitis shows proptosis on the left, a large globe, scleral enhancement, and dirty retrobulbar fat consistent with endophthalmitis and retroglobar infection.
Figure 2: MRI T2-weighted sequence obtained one month later demonstrates a small shrunken calficified globe, consistent with phthisis bulbi which has progressed since the prior examination. This is phthisis bulbi as a sequela of infection.
Figure 3: FLAIR image demonstrates bright signal in the left globe as compared with the normal low signal in the right globe related to fluid.


Diagnosis: Phthisis Bulbi secondary to endophthalmitis from Serratia meningitis


There is a predisposition to endophthalmitis seen in diabetics, patients with debilitating diseases or the immmunosuppressed. Once the intraocular infection is established, exudates are deposited in the vitreous humor along with inflammatory cell infiltration of the global wall (the sclera, choroid and retina).

Phthisis bulbi is a retracted, scarred shrunken globe. It may be the end result of infection (as in our patient), noninfectious inflammation, radiation, trauma or other insult. The globe is usually one half to one third the size of the normal size due to reduced aqueous production. Furthermore, the globe has a diffuse increase in density and demonstrates an irregular contour. There are diffuse calcifications, either mottled or linear within the globe and there may be ossification of the devitalized tissue. The separate structures within the globe are often distorted and cannot be discerned. There is frequently associated atrophy of the optic nerve. Blindness and shrinkage of the globe may occur even with aggressive intraocular injection of antibiotics.

CT is the modality of choice for demonstrating the soft tissue abnormalities and possible calcification of phthisis bulbi. Enhancement of the vitreous humor may indicate that the humor is the initial site of involvement.

Glioblastoma multiforme

Findings

Multiple enhancing masses with surrounding vasogenic edema and mass effect in the left cerebral hemisphere. There is associated sulcal effacement, gyral expansion/thickening, and mass effect with approximately 9-mm midline shift toward the right.


Diagnosis: Glioblastoma multiforme


Glioblastoma multiforme (GBM) is unfortunately both the most common and the most malignant of the glial tumors.
Of approximately 17,000 primary brain tumors diagnosed in the U.S. every year, 60% are glial tumors. Males have a slight predominance: 1.5 to 1.

The World Health Organization classification:
- Grade II: Low-grade diffuse astrocytoma
- Grade III: Anaplastic astrocytoma
- Grade IV: Glioblastoma multiforme

GBMs often arise in the subcortical white matter of the cerebral hemispheres. 31% arise in the temporal lobes. 24% arise in the parietal lobes. 23% arise in the frontal lobes and 16% arise in the occipital lobes. Sites such as the brain stem, cerebellum and spinal cord are much less common.
Classically, GBM has a thick, irregular enhancing ring of neoplastic tissue which surrounds a necrotic core.

The differential diagnosis for GBM includes:
- Abscess: Ring enhancement is usually thinner than GBM
- Metastases: Usually multiple lesions at gray-white junction
- Anaplastic astrocytoma: Usually nonenhancing white-matter mass. Enhancement may suggest degeneration to GBM
- Primary CNS lymphoma: Periventricular enhancing mass which often crosses the corpus callosum
- Tumefactive demyelination: Usually incomplete "horseshoe" enhancement which is open toward the cortex

Subclavian steal syndrome

Additional clinical information: Sixty-year-old man with left arm burning on use, noted to have decreased blood pressure in left upper extremity. History of prior left carotid endarterectomy.


Findings

Arteriogram demonstrates occlusion of the left subclavian artery origin with reconstitution of flow after approximately a 1-cm segment via the left vertebral artery. Findings are consistent with subclavian steal syndrome. The peripheral left common carotid artery has an approximately 40% diameter stenosis at the operative site.

Differential diagnosis - Causes of ubclavian steal syndrome:
- Atherosclerotic disease
- External compression
- Thrombosis
- Dissection
- Embolism
- Trauma


Diagnosis: Subclavian steal syndrome


Definition: Stenosis/obstruction of the subclavian artery near its origin with demonstration of ipsilateral vertebral artery flow reversal, compromising cerebral flow.
This can be either congenital or acquired secondary to atherosclerotic disease most often. Other causes of acquired steal can be secondary to trauma, embolism, tumor thrombosis, dissecting aneurysm, radiation, inflammatory arteritis, or ligation.
Incidence is 2.5% of all occlusions of extracranial arteries. Associated with additional lesions 81% of the time.
Males affected more often than females 3:1. Left-sided more often than right 3:1.

Signs and symptoms are:
- Weak or absent ipsilateral extremity pulse.
- Ipsilateral extremity has lower systolic blood pressure by >20-40 mm Hg.
- Evidence of brachial insufficiency (pain, coolness, numbness, burning, necrosis).
- Evidence of vertebrobasilar insufficiency (syncope, ataxia, vertigo, headache).

Angiographic studies show the occlusion/stenosis of the subclavian artery and can demonstrate the retrograde vertebral artery flow.
Color Doppler studies can demonstrate the reversal of the vertebral artery flow.
Treatment is surgical bypass or PTA
Occult subclavian steal syndrome is when the flow reversal can only be seen after maneuvers like ipsilateral arm exercise or inflation of blood pressure cuff.
Partial subclavian steal syndrome is when there is retrograde flow seen during systole and antegrade flow is seen during diastole.

Osteoporosis circumscripta

Findings

Figure 1: Axial CT image with bone windowing shows confluent areas of lysis involving the frontal bone and portions of both temporal bones with relative sparing of the cortex and thinning of the diploic space.
Figure 2: More cephalad axial CT image demonstrates involvement of the frontal bone and right parietal bone anteriorly.


Diagnosis: Osteoporosis circumscripta


Paget disease was first described by Sir James Paget in 1877 as osteitis deformans which later came to be known as Paget disease. It is the second most common bone disorder in the elderly population behind osteoporosis. The disease process has three phases, beginning with the lytic phase where exaggerated bone resorption occurs by atypical osteoclasts. This results in the second phase, or mixed phase, where morphologically normal osteoblasts move in and cause rapid increases in bone formation. The newly formed bone is disorganized, larger, weaker and more vascular. The final phase, or sclerotic phase, is when osteoblastic activity predominates with formation of thickened and enlarged sclerotic bone.

Osteoporosis circumscripta indicates involvement of the calvarium during the lytic phase of Paget disease and is characterized by asymmetric and confluent foci of calvarial lysis. The involved bone is usually thinner than the normal bone which helps to differentiate from other lesions which tend to expand the calvarium or destroy cortex.

Paget disease affects the axial skeleton, long bones and skull predominantly. The hands and feet are almost never involved. It is most commonly found in caucasian populations, mainly in the northeast and in Europe. The majority of patients are asymptomatic with the disease detected by an incidentally elevated alkaline phosphatase level or characteristic bone changes. The etiology is unknown with various hypotheses including a familial cause linked to chromosomes 6 or 18q. Infectious causes have also been theorized as biopsies from these patients demonstrate paramyxovirus antigens within osteoclasts.

Spinal cord herniation

Findings

Initial non-contrast sagittal T1 and sagittal T2 weighted images demonstrate anterior (ventral) displacement of the spinal cord from T4-T6 with enlargement of the subarachnoid space dorsally.
Sagittal reconstructed image from a CT myelogram (Figure 3) performed 15 days later shows a similar finding.
Axial images from a CT myelogram demonstrate anterior displacement of the spinal cord with enlargement of the subarachnoid space dorsally (Figure 4). We also see that the subarachnoid space is continuous and fills with contrast without evidence of an arachnoid cyst, as is often mistaken for the diagnosis.


Diagnosis: Spinal cord herniation


Spinal cord herniation is a rare diagnosis to be considered in patients presenting with slow and progressive neurologic symptoms.
CT myelogram helps to confirm findings on MRI.
Pathogenesis is unclear, however is thought to be related to an initial thoracic dural defect, whether congenital or acquired.

Spinal cord herniation is a rarely encountered cause of myelopathy. The pathogenesis of thoracic cord herniation has been ascribed to a dural defect, either congenital or acquired, on the convex ventral surface of the thoracic spinal canal. The spinal cord is believed to “plug” the hole in the dura, and prolonged CSF pulsations force the cord through the dural defect. Adhesions and distortion of the cord with possible vascular compromise over time leads to progressive myelopathy. This proposed mechanism explains the absence of idiopathic spinal cord herniation occurring in the cervical and lumbar spine and posteriorly in the thoracic spine, where the cord would not be so closely applied to a potential dural defect.

The clinical presentation in the literature of thoracic cord herniation is characteristic but nonspecific. Age of presentation ranges from 22-71 years old with a mean age of 43. There is also a 2:1 female to male ratio. A majority of herniations present with a Brown-Sequard syndrome (ipsilateral hemiparesis and loss of proprioception and vibratory sensation and contralateral loss of pain and temperature sensation). A minority may present with paraparesis or bladder and bowel dysfunction. The onset of symptoms is usually slow and progressive.

Imaging studies characteristically show the cord appearing small, rotated, and displaced with an apparently dilated CSF space opposite to the direction of cord displacement. This apparently dilated CSF space represents the void left by the herniated cord. In such cases, the CSF space would be expected to follow the signal characteristics of normal CSF on MRI sequences and to fill readily with intrathecal contrast material. This could also be interpreted as an expansive communicating arachnoid cyst compressing the cord or as spinal cord adhesions from posttraumatic or postoperative fibrosis that have tethered the cord to the dura against the wall of the spinal canal. Axial images may be helpful in distinguishing a compressed cord from a herniated cord, especially if the dural defect has allowed only the lateral portion of the cord to herniate into bony notches or defects. The most common location for thoracic spinal cord herniation is between T2 and T8 over a length of 1 to 3 cm.

Treatment includes surgical release of the incarceration with repair of the dural defect. The surgical defect in the dorsal dura may require a dural graft to provide a larger dural space, as the reduced spinal cord may be swollen and edematous. In the majority of cases in the literature, the patients’ neurologic deficits resolved or improved.

Balo's concentric sclerosis

Findings

Figure 1: T1-weighted image shows low density in both the posterior and the left anterior periventricular region.
Figure 2: T2-weighted image shows high signal in the periventricular lesions with suggestion of concentric rings of hyperintensity and isointensity.
Figure 3: FLAIR image reveals edema in the periventricular lesions.
Figure 4 and Figure 5: The postcontrast T1-weighted images show enhancement in a concentric ring like fashion and hold the key to the diagnosis.


Diagnosis: Balo's concentric sclerosis


Balo’s concentric Sclerosis (BCS) is a rare demyelinating disorder considered to be a variant of multiple sclerosis (MS).Histologically it is characterized by alternating rings of myelin preservation or remyelination and demyelination involving the cerebral hemispheres, brain stem, spinal cord, and optic chiasm. The clinical course of BCS is considered variable with the current treatment modalities.

The MR imaging findings show hypointense and isointense concentric bands on T1 weighted images, concentric hyperintense and isointense bands on T2 weighted images. The hyperintense bands on T2 weighted images correspond to concentric bands of demyelination with gliosis and perivascular lymphocytic infiltration. The isointense bands represent the white matter which has been spared or has had remyelination. On the post contrast T1 weighted images all the lesions showed concentric rings of enhancement, indicating rings of active inflamed and spared white matter.

It has been noted that with treatment and over a period of time, the contrast enhancement decreases and so does the size of the lesions. The characteristic concentric pattern may not be observed if the MR imaging is not performed early in the disease. Our patient is still in the hospital being treated with high dose steroids.

Differential for the imaging findings would include Marburg variety of multiple sclerosis, ADEM (Acute disseminated encephalomyelitis) and lymphoma. ADEM also has multiple lesions which enhance after gadolinium administration. The age of the patient does not favor that and the patient did not have history of any viral illness. Lymphoma should have more mass effect and more enhancement. The patient did not have any history of immunosuppresion.