Expanding Virchow Robin space in the midbrain causing hydrocephalus

Findings

Figure 1: Noncontrast CT brain image demonstrate a cluster of round cyst-like lesions in the right thalamic region with associated dilated 3rd and frontal horns of the lateral ventricles. Note the cyst-like lesions follow CSF attenuation. No evidence of calcification is seen.
Figure 2, Figure 3, Figure 4: Sagittal T1 weighted non-contrast images and axial T2 weighted images demonstrate a cluster of round cyst-like lesions in the midbrain/right thalamic region with associated aqueductal compression and hydrocephalus. The cyst-like lesions follow CSF signal intensity on all pulse sequences.
Figure 5: Coronal FLAIR images demonstrate a cluster of round cyst-like lesions in the midbrain/right thalamic region with associated aqueductal compression and hydrocephalus. The cyst-like lesions follow CSF signal intensity and attenuate completely on FLAIR images.
Figure 6: Coronal T1 weighted postcontrast image demonstrates a cluster of round cyst-like lesions in the midbrain/right thalamic region with associated aqueductal compression and hydrocephalus. The cyst-like lesions follow CSF signal intensity on all pulse sequences. No calcification or enhancement is seen.


Diagnosis: Expanding Virchow Robin space in the midbrain causing hydrocephalus


Pestalozzi and later Virchow in 1851 and Robin in 1859 characterized the perivascular space of Virchow-Robin. This is a pial-lined interstitial fluid – filled structure that accompanies penetrating arteries but does not communicate directly with the subarachnoid space. They affect 25-30% of the pediatric population. Mean age of occurance of enlarged PVSs in adults is mid 4th decade with a slight male preponderance. They occur at all locations and at all ages and are usually discovered incidentally. They occasionally present with non-specific symptoms such as headaches.

Normal PVSs are commonly seen in the basal ganglia region whereas giant or tumefactive PVSs are seen in the midbrain. Other common locations include deep white matter, subinsular cortex and extreme capsule. Less common sites include the thalami, dentate nuclei, corpus callosum and cingulate gyrus. They almost never involve the cortex. PVSs are usually 5mms or less. Occasionally they may enlarge up to several cms and may cause focal mass effect or obstructive hydrocephalus.

Imaging findings include clusters of round /ovoid/linear/punctuate cyst-like lesions which follow CSF density/signal intensity on all pulse sequences. They suppress completely on FLAIR images and show no restricted diffusion on DWI. They neither calcify nor enhance.

Differential diagnosis includes cystic neoplasm, lacunar infarct and infectious (neurocysticercosis, hydatid cyst) or inflammatory cysts. Enlarging PVSs are "DO NOT TOUCH" lesions unless they cause obstructive hydrocephalus where the patient needs to be shunted.

Graves disease

Findings

0.1 mCi of I-123 in the form of sodium iodide capsule was administered orally. 4 and 24 hour radioiodine uptakes were determined. The following day, 5.4 mCi of Tc 99m sodium pertechnetate was injected intravenously for the perfusion part of the scan followed by routine planar and pinhole imaging of the neck.

There is increased flow to the thyroid gland bilaterally. Planar and pinhole imaging of the neck demonstrate a symmetrically enlarged gland with homogenous radiotracer uptake. Thyroid to salivary gland ratio is increased and there is suppression of the background. Four-hour radioactive iodine uptake (RAIU) is 22.2% and 24-hour radioactive iodine uptake is 55.3%.



Diagnosis: Graves disease


Graves disease is the most common etiology of thyrotoxicosis and predominantly occurs in middle-age females. Binding of immunoglobulins to TSH receptors results in autonomous, inappropriate hyperfunctioning of the thyroid gland. This result in suppression of TSH levels, which are typically less than 0.01 mU/L.

Thyroid scintigraphy and RAIU determination are useful for distinguishing Graves disease from other causes of thyrotoxicosis in ambiguous cases. Thyroid scan radiotracers include Tc99m pertechnetate, I123 and I131. I123 is preferred over I131 for most applications due to the shorter half-life and lower peak energy of the I123 gamma photon, which results in more optimal image quality and lower radiation dose to the patient. Imaging is performed 2-6 hours after I123 is administered. Radioiodine distributes to the salivary glands, stomach and choroid plexus and is only stored within the thyroid. The classic thyroid scan findings associated with Graves disease include homogeneously increased activity in an enlarged thyroid gland, increased thyroid to salivary gland activity and suppression of the background. RAIU measurements can be performed at 4-6 hours and 24 hours. Graves disease usually yields RAIU values of 40 to 80% (normal 10 to 30%) at 24 hours. However, high-turn over varieties may manifest only as elevated 4-6 hour RAIU values (normal 4 to 15%), as 24 hour RAIU results may be normal or only mildly elevated.

Patients with Graves disease are initially treated with beta-blockers and temporarily with thyroid specific medications, such as PTU and methimazole. Radioiodine therapy, rather than surgery, represents the definitive treatment of choice. Indeed, high cure rates result from I131 treatment doses of at least 15 mCi. Side-effects for Graves treatment doses include hypothyroidism, radiation induced thyroiditis, xerostomia, sialadenitis, change in taste, and worsening of ophthalmopathy. Leukemia and other secondary malignancies are rare in any setting and not relevant to the Graves/hyperthyroid treatment doses

Anoxic/hypoxic brain injury

During initial triage, the patient had cardiac arrest and resuscitation







Five days later







Findings

No significant abnormality is noted on the first non-contrast CT head performed the day of the patient’s cardiac arrest. On the CT head performed five days later, however, there has been interval diffuse loss of gray-white differentiation, decreasing ventricular size, and decreasing sulcal prominence. In addition, at level/window shown, there is now subtle hypodensity of the caudate heads and lentiform nuclei bilaterally.

Differential diagnosis:
- Anoxia/hypoxia
- Toxic exposure
- Metabolic abnormalities


Diagnosis: Anoxic/hypoxic brain injury


Key points

A period of global intracranial hypoxia (hypoperfusion or hypoxemia) tends to affect the most metabolically active areas of the brain preferentially.
These areas include the caudate nuclei, lentiform nuclei, parahippocampal gyri, hippocampi, cerebellar hemispheres, and cerebral white matter.
A similar distribution of injury occurs with exposure to certain toxins like carbon monoxide, methanol, hydrogen sulfide, barbiturates, and Ecstasy.
Metabolic abnormalities like hypoglycemia can also cause injury to these structures and should be included in the differential.
CT findings include hypo densities in the affected areas representing edema, which later resolves leaving residual volume loss with possible calcification and/or hemorrhage.
Evidence of diffuse brain edema (loss of gray-white definition, sulcal effacement, effacement of cisterns, downward herniation, etc.) may be present acutely as well.
MR findings include increased signal on fluid sensitive sequences in the affected areas. Hemorrhagic necrosis (petechial or laminar) may subsequently develop.

Tuber cinereum hamartoma

Findings

There is a 1 cm circumscribed, exophytic mass extending from the hypothalamus in the region of the tuber cinereum. It is isointense to gray matter on both T1 and T2 sequences. There is no appreciable contrast enhancement.

Differential diagnosis:
- Tuber cinereum hamartoma
- Non-enhancing (low grade) glioma
- Craniopharyngioma
- Germinoma


Diagnosis: Tuber cinereum hamartoma


Key points

Tuber cinereum hamartoma is a non-neoplastic focus of heterotopic gray matter.
Clinically, patients present with precocious puberty (due to increase leutinizing hormone releasing hormone release) and/or gelastic seizure activity.
Of pathologically proven lesions, 75% of patients will have experienced precocious puberty and 25% will have experienced seizures.
In patients with precocious puberty, 33% will be found to have tuber cinereum hamartoma.
Imaging features include small size (1 cm), round shape, non-enhancing, location near tuber cinereum (between pons/mamillary bodies and posterior aspect of the optic chiasm), iso- to hypo-intense on T1 sequences, and iso- to slightly hyper-intense to gray matter on T2. These tumors DO NOT invade adjacent structures.

Eagle syndrome

Findings

Figure 1 : AP radiograph of the cervical spine demonstrates an asymmetric ossified structure extending from the left side of the skull base.
Figure 2 and Figure 3 : Axial CT image and a 3D reconstruction demonstrate an elongated left styloid process that extends to the level of the vallecula as can be seen in Eagle syndrome.


Diagnosis: Eagle syndrome


An elongated styloid process, as well as calcification of the stylohyoid ligament, can result in clinical symptoms, known as Eagle syndrome. In an adult, the normal length of the styloid process is 2.5 cm. It is considered elongated when 3 cm or greater. The etiology of this rare disorder is unknown. It tends to occur at an older age, and is more common in women. Although approximately 4% of the population is thought to have an elongated styloid process, only 4 – 10.3% of this group experience symptoms. Hence, an elongated styloid process may go unnoticed, unless it results in clinical symptoms. These symptoms may occur due to irritation of adjacent nerves, most commonly the glossopharyngeal, lower branch of the trigeminal, and chorda tympani nerves. Patients may experience throat or ear pain, taste disturbance or throat discomfort. Alternatively, symptoms may arise from local mass effect, such as dysphagia or a foreign body sensation.

The differential diagnosis for Eagle syndrome is vast, largely due to the varying types of symptoms that patients may experience. However, other entities to consider include migraines, neoplasms, temporal arteritis, laryngopharyngeal dysesthesia, Sluder syndrome, cluster type headaches, glossopharyngeal/trigeminal neuralgia, temporomandibular arthritis, hyoid bursitis and cervical vertebral arthritis. Imaging will distinguish between these entities and Eagle syndrome.

Diagnosis of Eagle syndrome involves both clinical and radiological means. On physical examination, a mass may be palpated in the tonsillar fossa. A lateral plain film of the cervical spine will reveal an asymmetric elongated and ossified styloid process. A CT scan is often obtained to help clarify the relationship between the styloid process and adjacent structures of the neck. Imaging may also reveal a calcified stylohyoid ligament. A barium study performed for dysphagia may show a filling defect due to the indentation caused by the elongated styloid process.

Treatment of Eagle syndrome is both medical and surgical. In patients with mild or moderate symptoms, treatments with NSAIDs or steroid injections may be adequate. Surgical intervention is used in patients with severe symptoms and involves surgical removal of the elongated portion of the styloid process. One of the most common complications with surgical removal is infection of the deep spaces of the neck, reduced via an extraoral approach.

Findings

Transverse (Figure 1) and sagittal (Figure 2 and Figure 3) ultrasound images of the left thyroid lobe demonstrate a nodule with multiple punctuate echogenic foci and associated comet-tail artifact. These represent colloid crystals and are a reliable ultrasonographic feature indicating a benign nodule. The comet-tail artifact distinguishes these echogenic foci from microcalcifications.


Diagnosis: Benign hyperplastic adenomatoid nodule of thyroid


Ultrasound is of great benefit in the management of thyroid nodules in that it is a noninvasive test, can identify suspicious features, determines the presence of other coexisting nodules in the gland, helps demonstrate lymphatic spread and can be used as a guide for percutaneous biopsy. There is considerable overlap in US features of benign and malignant thyroid nodules and no one sonographic finding is absolutely 100% specific or sensitive for malignancy. However, certain sonographic characteristics have been described as more suggestive of malignancy or benignity, and become especially helpful when multiple signs suspicious for malignancy are present.

Size, number and slight interval growth detected only on ultrasound are generally unreliable signs in deciding whether a nodule is malignant or benign.



US features suggestive of malignancy

1.Thyroid microcalcifications, or psammoma bodies, are one of the most specific findings for thyroid malignancy, and if present in a hypoechoic nodule are highly predictive of papillary carcinoma.
2.Large, coarse dystrophic calcifications from tissue necrosis are also associated with a high malignancy rate.
3.An ill-defined and irregular margin may hint at malignant infiltration into adjacent thyroid parenchyma, but this finding has a wide range of sensitivity and specificity.
4.A solid nodule that is taller than it is wide (greater AP to transverse dimension) may be potentially malignant, although this sign has not been widely described.
5.Intrinsic hypervascularity is seen in a majority of malignant nodules, but is not a very specific sign.
6.Malignant nodules typically have a solid and hypoechoic appearance, but again around half of benign nodules may have a similar appearance. Marked hypoechogenicity less than that of the strap muscles is more specific.


US features suggestive of benignity

1.The presence of inspissated colloid is a reliable sign of benignity and should be distinguished from microcalcifications using high frequency probes to demonstrate its characteristic reverberation artifact.
2.A thin, uniform hypoechoic halo is produced by a pseudocapsule of fibrous tissue and compressed thyroid parenchyma. Its presence is highly suggestive that a nodule is benign, however it is also seen in a small percentage of malignant nodules.
3.A predominantly cystic nodule is more likely to be benign. A cystic variant of papillary carcinoma has been described, but it is rare and close US examination will demonstrate malignant signs such as solid hypervascular component or microcalcifications.
4.Small subcentimeter cystic nodules represent benign colloid-filled cysts.
5.Peripheral calcifications are usually seen in benign multinodular thyroid, but may also be present in malignancy.


One must keep in mind that in the approach to a thyroid nodule, the decision to biopsy should be based not only on the sonographic characteristics of the nodule, but the findings need to be taken in context with physical exam findings, laboratory tests, and patient history. The age and sex of the patient, personal or family history of thyroid cancer, and prior history of neck irradiation are important considerations in a patient’s history that would lower the threshold for biopsy. Likewise a firm and fixed nodule, the concomitant symptoms of dysphagia or hoarseness, a rapidly growing nodule, and the presence of lymphadenopathy raise the likelihood a nodule may be malignant.

Atypical teratoid rhabdoid tumor (ATRT)

Findings

Figure 1, Figure 2, and Figure 3: There is a large solid/cystic left hemispheric mass with internal calcifications.
Figure 4, Figure 5, Figure 6, and Figure 7: T1, T2, FLAIR, and T1 post MR images demonstrate a large, solid/cystic left hemispheric mass with mild rightward subfalcine herniation, peripheral enhancement, and some adjacent edema.


Diagnosis: Atypical teratoid rhabdoid tumor (ATRT)


Atypical Teratoid Rhabdoid Tumor (ATRT) is a rare, highly aggressive intracranial mass found in infants and children under 3 years of age. Pathologically, rhabdoid cells within this tumor resemble those found in malignant rhabdoid tumor of the kidney. Divergent differentiation within the tumor accounts for the “atypical teratoid” designation. Most common presenting symptoms include lethargy, seizures, vomiting, and increasing head circumference. 50% are infratentorial, 40% are supratentorial in location. They are typically large, heterogeneous masses that commonly contain cysts, hemorrhage, and calcifications. 15-20% present with disseminated disease at the time of diagnosis and thus the entire CNS system, including the entire spinal canal, must be imaged at presentation to evaluate for leptomeningeal spread of tumor.

Differential diagnosis includes supratentorial PNET and ependymoma although it’s often impossible to distinguish between these with imaging alone. Histologically, the distinction between PNET and ATRT is often difficult for the pathologist as the presence of rhabdoid cells is relied upon as the histologic hallmark of ATRT, and these cells are only present in a minority of cases. Additionally, >70% of ATRT histopathology appears identical to PNET and thus certain immunohistochemical features such as presence of epithelial membrane antigen, vimentin, and smooth muscle actin positivity are used to distinguish ATRT from primitive neuroectodermal tumors. Always consider ATRT when a large brain tumor is found in a child less than 3 years of age.

Treatment includes surgical resection/debulking. Chemotherapy is largely ineffective against these tumors and radiation therapy is often not feasible due to the young age of the patients affected. Mean survival is approximately 6 months and overall 2yr survival is less than 15%.