Creutzfeldt-Jakob Disease - Sporadic form

Findings

Figure 1, Figure 2, and Figure 3: T2, DWI, and ADC map show increased signal and restricted diffusion in the basal ganglia. More specifically there is symmetrically increased signal in the caudate and putamen with sparing of the globus pallidus. Additional areas of increased signal are seen in the right and left parietal cortex (Figure 4). No contrast enhancement was seen.


Diagnosis: Creutzfeldt-Jakob Disease - Sporadic form


CJD is a progressive fatal neurodegenerative disorder caused by prion proteins accumulating within the neurons.

There are three forms of CJD. A familial form, a sporadic form, and a variant or iatrogenic. form. The sporadic form (sCJD) is identified in 85% of cases. No genetic or infectious cause can be identified in these patients.

The familial or genetic form (fCJD) is seen in 15% of cases. These cases are identified by DNA analysis of the PRPC gene mutations.

Though it receives the most media attention, the infectious variant or iatrogenic form (vCJD) is the rarest, accounting for 1% of cases.

Diagnosis is based on clinical presentation, EEG findings, and a positive CSF analysis showing 14-3-3 proteins. MRI is reported to have high sensitivity and specificity for the disease with characteristic symmetric signal abnormalities in the basal ganglia and cortical abnormalities. The caudate and putamen are the most frequently involved nuclei. Thalamic involvement is only seen in 14% of patients with the sporadic form. However, thalamic involvement is seen in 78-100% of the variant/iatrogenic forms of CJD. The globus pallidus is usually spared. Diffusion weighted sequences are the most sensitive. Abnormalities are also well seen on T2 and FLAIR weighted sequences. The basal ganglia and cortical lesions show increased signal on T2 and FLAIR with persistent restricted diffusion. The cause of the restricted diffusion is not completely understood.

No treatment is available for the disorder at this time. The clinical course is usually progressive and rapid with most patients expiring within six months to one year from the time of diagnosis.

Craniometaphyseal dysplasia

Findings

Marked thickening of the skull base with narrowing of all the neural foramina. Hydrocephalus.

Differential diagnosis:
- Craniometaphyseal dysplasia
- Frontometaphyseal dysplasia
- Craniodiaphyseal dysplasia
- Osteopetrosis


Diagnosis: Craniometaphyseal dysplasia


Discussion

Craniometaphyseal dysplasia is a rare genetic disorder whereby stromal cells are not able to differentiate osteoclast precursors, resulting in craniofacial and long bone abnormalities and cranial nerve palsies.
Autosomal dominant form has variable expression. Autosomal recessive is more severe.
Radiologic findings include hyperostosis of the skull base, narrowing of the neural foramina which exit the skull base, and fraying or "celery stalking" of the metaphyses, usually in the lower extremities.
These children have normal growth, normal intelligence, no bone fragility and no growth retardation.

In this particular case:
- This patient has had bilateral cranial nerve VII decompression secondary to bony overgrowth of the neural pathway. This patient also has optic canals which are 50% smaller than normal
- This patient developed new hydrocephalus due to stenosis of the jugular foramina. The resultant venous hypertension created hydrocephalus by disturbing the pressure gradient which is necessary for CSF drainage into the venous system

Other dysplasias similarly affecting parts of the skull:
- Craniodiaphyseal dysplasia: children have mental retardation, massive sclerosis of the skull, retarded growth
- Frontometaphyseal dysplasia: X linked, hyperostosis of the skull base and vertex, mandibular hypoplasia, sinus obliteration

Central neurocytoma

Findings

Figure 1: T2-weighted axial image demonstrates a heterogeneous, intraventricular mass with cystic regions.
Figure 2 and 3: Axial FLAIR images demonstrates an intraventricular mass abutting the septum pellucidum with increased FLAIR signal.
Figure 4, Figure 5, Figure 6, and Figure 7: Postcontrast T1-weighted images demonstrate a heterogeneously enhancing lesion that abuts the septum pellucidum.

Differential diagnosis:
- Central (intraventricular) neurocytoma
- Ependymoma
- Subependymal Giant Cell Astrocytoma (SGCA)
- Choroid plexus papilloma
- Meningioma
- Oligodendroglioma


Diagnosis: Central (intraventricular) neurocytoma


Although central neurocytomas account for less than 1% of all intracranial neoplasms, they constitute approximately 50% of intraventricular tumors in patients 20-40 years old. Most present with headache, signs and symptoms of increased intracranial pressure, seizure, or change in mental status. In rare cases tumors with neurocytoma features may involve the brain parenchyma or spinal cord and are referred to as extraventricular central neurocytomas. These have a worse prognosis.

There is controversy regarding whether the embryological origin of central neurocytomas arises from neuronal or bipotential progenitor cells. They have a more benign appearance with uniform round cells with neuronal differentiation. Anaplastic features and necrosis is rare. Histologically, central neurocytomas are difficult to distinguish from oliogodendrogliomas, and immunohistochemical staining for synaptophysin and neuron specific enolase (positive in neurocytoma) is used to differentiate the two. They are considered as WHO grade II astrocytomas.

CT demonstrates a mixed solid and cystic lesion within the lateral ventricle with moderate, heterogeneous enhancement. Most lesions occur in the body or frontal horns of the lateral ventricle or near the foramen of Monro. This can result in obstructive hydrocephalus. Calcification occurs in 50-70% of cases. On MR the lesion is heterogeneous with the majority of the lesions being isointense to gray matter on T1 and the cystic regions being hypointense on T1 and hyperintense on T2. Prominent flow voids can also be seen. On FLAIR sequences the mass is heterogeneous and predominantly hyperintense. Contrast enhanced MR is the preferred imaging modality in these cases. MR spectroscopy demonstrates a large choline peak. Central neurocytomas typically demonstrate decreased activity on PET imaging.

Most central neurocytomas are treated with complete surgical resection, which is usually curative. These tumors are typically benign and rarely invade brain parenchyma or develop local recurrence. In cases of local recurrence or incomplete resection radiation therapy, chemotherapy, and/or radiosurgery can be employed as adjunct treatments. Overall the 5 year survival rate is over 80%.

Cerebellar pontine angle meningioma

Findings

Broad based extra-axial mass located in the left cerebellar pontine angle extending to the porous acousticus but not entering the internal auditory canal. The mass demonstrates isointensity relative to gray matter on T1-weighted and mildly increased signal on T2-weighted sequences. The mass enhances homogeneously with contrast. There is moderate mass effect on the brachium pontes.

Differential diagnosis for a cerebellar pontine angle (CPA) mass:
- Meningioma
- Schwannoma
- Dermoid
- Epidermoid
- Metastasis
- Sarcoid
- Arachnoid cyst
- Lipoma
- Aneurysm


Diagnosis: Cerebellar pontine angle meningioma


Discussion

CPA meningiomas are often positioned eccentric to the porous acousticus

CT findings: NECT
- 70% hyperdense, 30% isodense; 25% calcified
- Hyperostosis or permeative bone changes
- IAC flaring
+ CECT: 90% strong uniform enhancement, 10% inhomogeneous

MRI findings (See table below)

Angiography
- Dural vessels supply tumor center and pial vessels supply the rim
- Sunburst pattern of enlarged dural feeders
- Vascular stain in venous phase
- Arteriovenous shunting may be present

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