Grade III IVH

Findings

Coronal plane through frontal horns. Echogenic structures are seen on both sides, just posterior to the frontal horns. An arrowhead points to the echogenic material on the left which may either be in the subependymal area or within the ventricle. Orthogonal parasagittal or transcranial axial views may help differentiate between these possibilities. An arrow points to echogenic material, probably a clot in the temporal tip.
Coronal plane through lateral ventricles. A more posteriorly angulated view than Fig 1 shows the right and left lateral ventricles filled with heterogeneous material. This material consists both of homogeneously echogenic choroid and echopenic, and therefore subacute, clot. Acute clot is homogeneously echogenic similar to normal choroid plexus. Choroid plexus, however, is not seen anteriorly in the frontal horns, ie, anterior to the foramen of Munro.
Parasagittal plane through right lateral ventricle. The orthogonal view helps prove the clot is within a dilated lateral ventricle consistent with a Grade III hemorrhage. An arrowhead points to homogenous echogenic choroids inferior to the clot and not seen extending anterior to the foramen of Munro area, which can be estimated at about midthalamus. In addition, color Doppler can show vascular flow in normal choroid plexus but not in clot.


Diagnosis: Grade III IVH


Premature neonates, particularly those less than 1500 grams or less than 32 weeks gestational age, are at risk for subependymal and intraventricular hemorrhage. Essentially all these hemorrhages develop from bleeding from single-cell thick vessels in the subependymal area of the brain found between the head of the caudate nucleus and thalamus.

A number of years ago, Papille et al created a grading system for hemorrhages that has its proponents and detractors. It however remains an adequate method of communicating areas involved by intracranial subependymal hemorrhage.

Grade I hemorrhage consists of hemorrhage within the subependymal area. Older or resolved Grade I hemorrhages may be imaged as cysts in the subependymal area. This is not the only reason for the development of subependymal cysts.
Grade II hemorrhages extend from the subependymal area into the lateral ventricle with little, if any, ventricular dilatation.
Grade III hemorrhage is intraventricular hemorrhage with dilatation of the involved lateral ventricle.
Grade IV hemorrhages were once thought of as extensions of Grade III hemorrhages into the surrounding brain parenchyma.

In the late 1980s Volpe, noting a difference in timing for the development of echogenic, cystic, or mixed echogenicity areas in the brain compared to the earlier presence by 1-2 days of clot in the ventricle suggested that the intraparenchymal portion of the Grade IV IVH was due to associated venous infarction.
Patients with Grade I and II hemorrhages usually do well clinically. The results for more severe Grade III and IV hemorrhages is less good.

Giant parietal foramina

Findings

Scout view (lateral view) from a CT scan reveals a large, well-defined parietal calvarial defect.
Brain and bone windows demonstrate bilateral parietal large and symmetric rounded calvarial defects (Figures 2 and 3).
3D surface-shaded reconstructed CT shows to better advantage the 3D characteristics of the calvarial defects and also reveals sagittal and coronal suture synostosis.


Diagnosis: Giant parietal foramina


Giant parietal foramina (GPF) are also known as foramina parietalia permagna, fenestrae parietals symmetricae, enlarged parietal foramina, Catlin marks, and cranium bifidum. GPF is associated with cerebral venous and cortical anomalies, gentic syndromes, and gene mutations. GPS can be an isolated entity, or be inherited in an autosomal dominant fashion. Gene mutations have been linked to both GPS and craniosynostosis. The calvarial defects can be repaired by bone grafts and mesh plating systems in patients at risk for injury to protect the underlying brain from trauma.

There is essentially no differential diagnosis for giant parietal formaina if a good clinical history is obtained (no prior craniectomy, trauma, soft tissue mass associated with the defects, etc). This case illustrates the importance of recognizing the entity of giant parietal foramina. The radiologist should be aware of possible associated intracranial abnormalities such as cortical/cerebral venous anomalies that would be amenable to MRI, MRV, or CTV workup; 3D CT can be very helpful if there is any contemplation of surgical repair.

Epidermoid

Findings

Figure 1 (T1 axial) and Figure 2 (T1 post-gadolinium contrast): Lesion is slightly hyperintense to but near CSF intensity. It arises inferior to the fourth ventricle with mass effect on the adjacent cerebellum and brainstem and encroaches on the foramen magnum. Post-contrast imaging of the mass demonstrates no appreciable enhancement.
Figure 3 (T2 axial): The lesion is hyperintense on T2-weighted imaging and is of CSF intensity.
Figure 4 and Figure 5 (FLAIR): The lesion shows some mixed signal on FLAIR imaging.
Figure 6 The lesion demonstrates restricted diffusion on diffusion-weighted imaging.


Diagnosis: Epidermoid


Epidermoids compose approximately 0.2%-1.8% of all intracranial tumors. Epidermoid is a congenital CSF-like mass that is also known as a congenital epidermal inclusion cyst. This mass of epithelium arises from inclusion of ectodermal rest cells during neural tube closure at the third to fifth week of embryogenesis. They are slow-growing, well-circumscribed, smooth or lobulated lesions. Histologically, they have an internal layer of stratified squamous epithelium with a whitish fibrous capsule; given these features, epidermoids are often called a pearly tumor. Keratin and cholesterol crystals are identified within them.

Epidermoids grow slowly, and do not present until ages 20-60, peak age 40, in men and women equally. They typically present with headache or neuropathy (cranial nerves V, VII, VIII most commonly involved), and symptoms depend upon location. Most present in an intradural location, and almost half present in the cerebellopontine angle (40%-50%). Epidermoids are the third most common cerebellopontine angle mass after vestibular schwannoma and meningioma. As in this case, epidermoids may present around the fourth ventricle (17%). They may also present in the parasellar/middle cranial fossa (10%-15%), and 10% may present in an extradural location within the skull or spine.

On CT, epidermoids are typically low density and expand to fill the CSF space, insinuating around normal brain structures and appearing similar to arachnoid cysts. Epidermoids demonstrate variable appearance on T1-weighted imaging, based upon protein and lipid content, and they do not enhance after contrast administration.

Since epidermoids, like arachnoid cysts, may be similar to CSF signal on T1- and T2-weighted imaging, diffusion imaging is useful to differentiate these entities. Since arachnoid cyst contains CSF, and CSF does not present restriction to the diffusion in any direction, arachnoid cyst is dark on diffusion. In contrast, since epidermoids (like cholesteatomas) are composed of epithelial cells that grow in layers in an organized spatial organization, they present with markedly restricted diffusion and bright signal on diffusion. In addition, epidermoids are characteristically brighter on FLAIR imaging because of incomplete nulling to suggest a solid tumor (arachnoid cysts are dark like CSF).

Treatment includes microsurgical resection. Since epidermoids often insinuate through adjacent normal brain structures, surgery is often complicated and recurrence is common if the mass is not completely removed. Subarachnoid dissemination of contents and malignant degeneration to squamous cell carcinoma are rare.

Arachnoiditis ossificans

Findings

Sagittal T1 (Figure 1) weighted MRI image of the lumbar spine with poorly defined nerve roots of the cauda equina. A bony fusion mass is noted posteriorly from prior remote bony fusion surgery.
Sagittal T2 (Figure 2) weighted image demonstrates heterogeneous mixed low T2 signal within the thecal sac at multiple levels.
Axial T1 (Figure 3) weighted image with poorly defined and "clumped" nerve roots.
Axial T2 (Figure 4) weighted image with heterogeneous mixed low T2 signal.
Axial noncontrast CT (Figure 5) image of the lumbar spine reveals extensive intrathecal calcification.
Sagittal reconstructed noncontrast CT (Figure 6) of lumbar spine demonstrates widespread intrathecal calcification and "clumped" nerve roots.


Diagnosis: Arachnoiditis ossificans


Arachnoiditis has many causes including prior surgery, myelographic contrast agents (especially oil-based contrast agents used in past), infection, subarachnoid hemorrhage, and inflammatory disease (ie, sarcoidosis). Lymphoma, carcinomatous meningitis, Guillain-Barre, and CMV radiculitis can also cause nerve root thickening. Chronic endstage archnoiditis results in arachnoiditis ossificans. Patients with arachnoiditis ossificans often have progressive neurologic deficits.

This case illustrates the importance of noncontast CT in evaluation of arachnoiditis ossificans, since MRI can demonstrate variable T1 and T2 signal characteristics.

Schizencephaly

Findings

There are bilateral complete clefts in the posterior frontal parietal regions, with the lateral ventricles communicating openly with the subdural space. These clefts are lined with gray matter (polymicrogyria). The septum pellucidum is absent, and the corpus callosum is hypoplastic.


Diagnosis: Schizencephaly


Schizencephaly is a disorder of neuronal migration during embryogenesis of the brain in which clefts extend from the lateral ventricles to the pia. These clefts are lined by gray matter, may be unilateral or bilateral, and range in size from small slits to large gaps in the surrounding cerebral hemisphere. The etiology is unknown, but its frequent association with other disorders, including heterotopic gray matter, dysplasia of the corpus callosum, and absence of the septum pellucidum, points to a common error in migration. Other associations include the presence of arachnoid cysts, mega cisterna magna, and calcifications (best seen on CT). Clinically, epilepsy has been reported in 50-80% of cases of schizencephaly, more commonly in association with unilateral than with bilateral clefts; but the seizures tend to begin earlier and have a worse outcome with bilateral defects. The most common clinical finding is of asymmetrical muscle tone, which ranges from asymptomatic to paraparesis; increasing severity is associated with frontal location and bilaterality of clefts. Delay in motor skills, language deficits (more common in temporal defects), and hydrocephalus are also frequently encountered. MR is the modality of choice for diagnosis and for differentiation from porencephaly. The key finding is that the cleft is lined by gray matter, which is pathognomonic for schizencephaly. Other disorders of migration that may demonstrate enlarged or joined ventricles include lissencephaly and holoprosencephaly.

Holoprosencephaly

Findings

Figure 1: The image shows a fetus with only a single cerebral ventricle. Its thalami are fused. The findings are suggestive of holoprosencephaly, especially alobar.
Figure 2:The image of the anterior face shows a single nostril suggesting a midfacial anomaly. Holoprosencephaly is often associated with midline facial anomalies.


Diagnosis: Holoprosencephaly


Holoprosencephaly is a malformation sequence involving the brain and often the face. It is a disorder of brain diverticulation resulting in partial or complete failure of cerebral hemisphere cleavage. Failure of cleavage results in failed formation of midline cranial structures. Midline brain development is associated with midface development and hence holoprosencephaly is associated with midface anomalies. Noncleavage of the primitive forebrain (the prosencephalon) leads to noncleavage in all planes. Associated olfactory and optic bulb anomalies occur because the prosencephalon, the primitive forebrain, does not cleave in a horizontal plane. A lack of proper cleavage in the transverse plane leads to improper formation of the telencephalon and diencephalon, which leads to abnormalities of thalamus and hypothalamus development. The often-seen fused or noncleaved thalami, as in the test case, may be a consequence. Finally, abnormal cleavage in a sagittal plane leads to abnormalities of the telencephalon, which normally forms the paired cerebral ventricles. In such patients an interhemisopheric fissure and other midline structures will not exist. The anomaly develops between the fourth and eighth week of embryonic life, well before the structures of the fetal brain can be adequately imaged by antenatal US. The abnormality is found in 1 in 16,000 live births, but in a larger number of fetuses and an even larger number of embryos (as high as 1 in 250), many of whom do not survive the pregnancy, hence affecting the numbers found among living births. There is a 12% recurrence rate for nonchromosomal cases.

Cases of holprosencephaly are divided into 3 forms. The most severe form, alobar holprosencephaly, typically results in a single holosphere (rather than 2 brain hemispheres), a single ventricle which often communicates with a dorsal sac, and fused thalami. There is no third or fourth ventricle, falx, corpus callosum, or interhemispheric fissure. The midbrain, brainstem, and cerebellum are typically normal unless made hypoplastic by mass effect of the large monoventricle or dorsal sac.

The intermediate form, ie, semilobar holoprosencephaly, shows at least partial prosencephalon cleavage. Temporal and occipital lobes may be separated. There may be a rudimentary interhemispheric fissure or a posterior falx. The incomplete form of holoprosencephaly, known as lobar holoprosencephaly, is the least devastating and may have a relatively normal appearing brain. There may simply be an absent septum pellucidum with an evident corpus callosum and perhaps fused or squared frontal horns. Rostral fusion may be the only ventricular abnormality with atria, occipital horns and temporal horns apparently normal.

When a child is born with a midline facial anomaly, a head US is performed to rule out holoprosencephaly. Facial abnormalities in cases of holoprosencephaly are variable. There may be none, or mild dysmorphism, such as hypotelorism or bilateral median cleft lip or palate. Cebocephaly, an intermediate form, has hypotelorism and a single nostrilled nose. Ethmocephaly is a more severe form of facial anomaly with severe hypotelorism, arhinia, and an interorbital single or double proboscis. Other severe abnormalities include cyclopia with variable eye and nose pairings. More significant facial anomalies are almost always associated with alobar holoprosencephaly.

Holprosencephaly is usually a terrible diagnosis no matter what its form. Those with severe brain abnormality, especially with arhinia or choanal atresia, die soon after birth if they survive the pregnancy. Less severely affected individuals may live several years but usually have severe neurologic and intellectual impairment. Even those with lobar holoprosencephaly who may live a normal lifetime may be severely retarded.

Marchiafava-Bignami syndrome

Additional clinical history: The patient is an alcoholic.


Findings

CT shows mild prominence of the ventricles and sulci consistent with mild generalized cerebral volume loss. There is hypodensity involving the entire anterior and posterior corpus callosum. There are no intra or extra-axial fluid collections, midline shift, or mass effect. The basilar cisterns are patent. MRI shows abnormal T2 prolongation involving the entire genu and splenium of the corpus callosum. On T1, there is low signal intensity in the corpus callosum. On other images (not shown) there was no abnormal enhancement of the corpus callosum, and there was increased signal in the corpus callosum on diffusion weighted imaging.

Differential diagnosis for corpus callosum lesions:
- Ischemia
- Lymphoma
- Gliobastoma multiforme
- Metastasis
- Demyelinating disorders (MS, ADEM, PML)
- Marchiafava-Bignami syndrome
- Trauma shearing injury
- Toxoplasmosis


Diagnosis: Marchiafava-Bignami


Key points

Alcoholic patients and others with nutritional deficiencies may sustain demyelination of the corpus callosum, which may be considered a variant of extrapontine myelinolysis. It may also be more extensive and involve other brain regions. In an alcoholic patient with sudden onset of encephalopathy, this diagnosis should be considered. Marchiafava-Bignami syndrome is characterized by demyelination and central necrosis of the corpus callosum, often presenting with seizures, neurologic dysfunction, and coma. This is a rare syndrome with approximately 150 reported cases in the literature. There is a high incidence of mortality with this disorder. There is a subacute form which displays sudden onset of dementia progressing to the chronic vegetative state and a chronic form characterized by progressive dementia and a disconnection syndrome. The genu and splenium are often involved in the acute form and the body in the chronic form. Treatment is largely supportive and IV thiamine may be of some benefit.


Radiological overview

On non-contrast head CT, there will be hypodensity involving corpus callosum.

On MRI, there will be low T1 signal intensity in the corpus callosum due to edema and cystic change. There will be high signal predominantly in the genu and splenium on T2 weighted images. Diffuse weighted images are positive in the acute form signifying restricted diffusion and ischemic injury.