MR imaging findings of siderosis are pathognomonic. T2-weighted and, in particular, gradient-echo susceptibility imaging reveals characteristic hypointensity along the pial surface/subarachnoid space of the brain. Frequently, there is associated cerebellar atrophy.

Huntington’s disease, chorea, or disorder (HD), is a is a relentlessly progressive, fatal  neurodegenerative genetic disorder. It is typically an adult-onset, autosomal dominant inherited disorder. Juvenile form of HD (ie, onset of HD in patients younger than 20 years) accounts for approximately 5-10% of all affected cases.

The most striking neuropathology in HD occurs within the neostriatum, in which gross atrophy of the caudate nucleus and putamen occurs.

Clinically the disorder include, movement disorder, a cognitive disorder, and a behavioral disorder. Chorea is the most common movement disorder.

On imaging, HD presents with atrophy of the caudate nuclei resulting in “ballooning” of the frontal horns. Putaminal atrophy is often associated. Corresponding hyperintensity signal of the affected nuclei is often present on T2WI and FLAIR.

The differential considerations include: encephalocele, meningomyelocele, and teratoma. Teratomas are typically solid in nature. Encephaloceles have associated calvarial abnormalities and may contain brain tissue. Meningomyeloceles are most of the time encountered in the lumbar region.

Patients are symptomatic when compensatory flow to the subclavian artery from the vertebral artery diverts too much flow toward the arm and away from intracranial structures. In SSS patients, risk of stroke is poorly documented but seems low, around 9 percent, however symptoms can be debilitating.

Doppler examination of the vertebral arteries typically shows reversed flow on the affected vessel. Contrast enhanced MRA of the neck shows focal stenosis involving the left subclavian artery proximal to the take off of the vertebral artery. The corresponding axial 2 D time of flight shows no flow signal from the left vertebral artery.

The most common initial symptom is ipsilateral headache. Most of these (60 percent) are orbital or periorbital. They may also produce sudden onset of severe pain over the carotid (carotidynia). Incomplete Horner syndrome due to involvement of plexus around the ICA may occur. MRI shows enlarged vessel due to intramural hematoma that is hyperintense of T1 WI (particularly on T1 fat Sat). Narrowing of the lumen can also be seen.

Most dissection starts at about 1 or 2 cm distal to ICA origin.

Optimal treatment has not been determined. For cases without bleeding, heparin then coumadin are used.

Natural history is not well known. Many patients with minor symptoms may not present and presumably do well. In one series 75 percent of patients returned to normal, 16 percent had minor deficit and 8 percent had major deficit or died.

Typical MRI findings include: subdural fluid collections, enhancement of the pachymeninges, engorgement of venous structures, pituitary hyperemia, and “sagging” of the mid brain. CT myelography of the entire spine has been shown to be helpful in determining the location and extent of a CSF leak.

In some milder cases of SIH, the condition can resolve spontaneously. However, in  more serious cases this will require an epidural blood patch.

Cisternography is performed by introducing Indium-111-DTPA intrathecally via a lumbar puncture. Images are typically acquired at 6, 24 and 48 hours. In normal subjects, the tracer will rise to the basal cisterns in 1 to 3 hours,  giving the “Neptune’s triumvirate” or “trident” appearance reflecting radiotrace in the interhemispheric and Sylvian fissures The tracer will then proceed to flow over the convexities collecting in the sagittal area in 12 to 24 hours. The lateral ventricles are normally not visualized. A small amount of activity in the lateral ventricles within the first 24 hours can be seen in a small percent of normal subjects and is generally disregarded. Persistent activity within the lateral ventricles after 24 hours is virtually diagnostic in the proper clinical setting.

In patients with normal pressure hydrocephalus, there usually is ventricular “reflux” of the radiotracer, which persists for 24-48 hours or more. Little or no activity is seen over the cerebral convexities. This test is helpful when positive but of little value if negative.

MRI examination typically show communicating hydrocephalus with the ventricular system dilated out of proportion to the degree of volume loss distinguishing it from the usual age related volume loss. Ill defined often bilateral periventricular hallo of T2 hyperintensity signal can be seen representing subependymal CSF resorption. Also a prominent aquaductal flow void may be encountered especially with conventional spin echo proton density–weighted technique.

Being an oiled based contrast media, pantopaque is best evaluated by MRI showing signal similar to fat on all sequences, even saturating on fat suppressed MRI. Care should be taken not to confuse pantopaque with intrathecal lipoma.

“Herniated discs may take the form of protrusion or extrusion, based on the shape of the displaced material.

Protrusion is present if the greatest distance, in any plane, between the edges of the disc material beyond the disc space is less than the distance between the edges of the base in the same plane. The base is defined as the cross-sectional area of disc material at the outer margin of the disc space of origin, where disc material displaced beyond the disc space is continuous with disc material within the disc space. In the cranio-caudal direction the length of the base cannot exceed, by definition, the height of the intervertebral space.

Extrusion is present when, in at least one plane, any one distance between the edges of the disc material beyond the disc space is greater than the distance between the edges of the base in the same plane, or when no continuity exists between the disc material beyond the disc space and that within the disc space. Extrusion may be further specified as sequestration, if the displaced disc material has lost completely any continuity with the parent disc.

The term migration may be used to signify displacement of disc material away from the site of extrusion, regardless of whether sequestrated or not. Because posteriorly displaced disc material is often constrained by the posterior longitudinal ligament, images may portray a disc displacement as a protrusion on axial sections and an extrusion on sagittal sections, in which cases the displacement should be considered an extrusion. Herniated discs in the cranio-caudal (vertical) direction through a break in the vertebral body end-plate are referred to as intravertebral herniations.

Disc herniations may be further specifically described as contained if the displaced portion is covered by outer anulus, or uncontained when absent any such covering. Displaced disc tissues may also be described by location, volume, and content.

There classically are two forms of HS: a severe form, or type A, (usually diagnosed between 2 and 4 years of age), and a milder form, or type B (usually diagnosed around the teenage years). Suggestive clinical features may include coarse faces including thickening of the lips, tongue and nostrils, a short stature, bony deformities, organomegaly, joint stiffness, vision loss or impairment and mental retardation. Atlantoaxial subluxation may occur as a result of transverse ligament laxity or hypoplasia or absence of the dense. Flexion extension views are necessary. Another cause of cord compression is dural thickening from intradural collagen and mucosaccharidoses deposition usually at C1-C2 as in our case. The vertebral bodies may show a wedge-shaped appearance with blunted spinous processes.