Balo's Concentric Sclerosis

Balo's Concentric Sclerosis is an uncommon demyelinating disease.
It is characterized by alternative bands of demyelination and myelin preservation, often in whorl-like configurations.

Here T2 and postcontrast T1W images showing a large lesion in the left hemisphere with alternating T2-hyperintense and isointense bands.
On the T1W images after gadolinium there is alternating linear enhancement.
There is a smaller, similar lesion on the right.

LETM MRI (longitudinally extensive transverse myelitis)

Detection of a LETM spinal cord lesion associated with acute myelitis is the most specific neuroimaging characteristic of NMOSD (>3 vertebral segment longitudinally extensive transverse myelitis lesions)

(LETM) in NMO

Such lesions typically involve
—the central gray matter—cord swelling, —central hypointensity on T1- weighted sequences, and —enhancement following IV gadolinium administration; —extension of a cervical lesion into the brainstem is characteristic.

LETM pattern is characteristic of NMOSD - —7%–14% of initial and 8% of subsequent myelitis attacks in AQP4-IgG-seropositive patients do not meet the LETM definition.

LETM MRI pattern may also occur in patients with
infectious,
granulomatous,
neoplastic, and
paraneoplastic diseases,
acute disseminated encephalomyelitis (ADEM),
spinal cord infarction,
and dural arteriovenous fistula

Adson's sign

ADSON'S SIGN

 

Adson's sign is the loss of the radial pulse in the arm by rotating head to the ipsilateral side with extended neck following deep inspiration. This is accompanied by compression of the Subclavian artery by a cervical rib or tightened anterior and middle scalene muscles. Thoracic outlet obstruction may be caused by a number of abnormalities, including degenerative or bony disorders, trauma to the cervical spine, fibromuscular bands, vascular abnormalities, and spasm of the anterior scalene muscle. Symptoms are due to compression of the brachial plexus and subclavian vasculature, and consist of complaints ranging from diffuse arm pain to a sensation of arm fatigue, frequently aggravated by carrying anything in the ipsilateral hand or doing overhead work such as window cleaning.

Performed as follows

1. Patient in upright position.
2. Passively extend, abduct and externally rotate affected arm while palpating the radial pulse.
3. Ask patient to take a deep breath and hold it in.
4. Ask patient to extend neck and rotate the head towards affected side.

The test is positive if there is a marked decrease, or disappearance, of the radial pulse. It is important to check the patient's radial pulse on the other arm to recognize the patient's normal pulse. It is/was sometimes used as a sign of thoracic outlet syndrome (TOS). Adson's sign is no longer used as a positive diagnosis of TOS since many people without TOS will show a positive Adson's.

There is minimal evidence of interexaminer reliability.

It is named after Alfred Washington Adson.

Brown syndrome

1. Brown syndrome is a rare form of strabismus characterized by limited elevation of the affected eye.  It is a mechanical problem in which the superior oblique muscle/tendon (on the outside of the eyeball) is unable to lengthen and therefore does not move freely. This makes looking up and in with the affected eye difficult. Often the higher eye is mistakenly presumed to be the abnormal eye, but it is actually the lower eye that is affected. Brown syndrome causes the affected eye to have trouble looking upward and inwards towards the nose. Essentially the affected eye is “tethered” or held down by the tight superior oblique tendon.The disorder may be congenital (existing at or before birth), or acquired.Acquired Brown syndrome is uncommon but may be seen following surgery, after trauma or in association with inflammatory diseases. Trauma can cause a Brown Syndrome if a blunt object hits the eye socket in the upper inside corner near the nose. Surgery for the eyelid, frontal sinus, eyeball (retinal detachment) and teeth (dental extraction) have been linked to acquired Brown syndrome. Inflammation of the tendon-trochlea complex (from adult and juvenile rheumatoid arthritis, systemic lupus erythematosus and sinusitis) can be associated with development of the problem. Sometimes the cause is never identified.Hereditary cases of Brown syndrome are rare. Most cases arise without a family history (sporadic).
2. Harold W. Brown characterized the syndrome in many ways such as:

   • Limited elevation in the eye when head is straight up
   • Eyes point out in a straight up gaze (divergence in up gaze)
   • Widening of the eyelids in the affected eye on adduction
   • Head tilts backwards (compensatory chin elevation to avoid double vision)
   • Near normal elevation in abduction.

   
   

   Brown syndrome can be classified according to severity. In mild cases there is a reduced ability to look up and in with the affected eye. In moderate cases, there is also a tendency for the eye to move downward as it moves inward. In severe cases there is a tendency for the affected eye to turn downward when the patient looks straight ahead.
3. In Brown's original series there was a 3:2 predominance of women to men. Ninety percent of patients have only one affected eye, more commonly the right. Treatment recommendations for Brown syndrome vary according to the cause and severity of the movement disorder. Close observation alone is usually sufficient in mild cases. Visual acuity and the ability to use both eyes at the same time (binocular vision) should be monitored closely in young children. Nonsurgical treatment is often advised for recently acquired, traumatic and variable cases. Systemic and locally injected corticosteroids have been used to treat inflammatory cases of acquired Brown syndrome. Non-steroidal anti-inflammatory agents (like ibuprofen) have also been used. Surgical treatment is usually recommended if any of the following are present: eye misalignment when looking straight ahead, significant double vision, compromised binocular vision or pronounced abnormal head position. More than one surgery may be needed for optimal management.The goal of surgery is to restore free ocular rotations. Various surgical techniques have been used:
• Harold Brown advocated that the superior oblique tendon be stripped. A procedure named sheathotomy. The results of such a procedure are frequently unsatisfactory because of reformation of scar tissue.
• Tenotomy of the superior oblique tendon (with or with out a tendon spacer) has also been advocated. This has the disadvantage that it frequently produces a superior oblique paresis.
• Weakening of the inferior oblique muscle of the affected eye may be needed to compensate for iatrogenic fourth nerve palsy. 

1. It's also known as Superior Oblique Tendon Sheath syndrome. Not to be confused with Brown-Vialetto-Van Laere syndrome.

Cerebral perfusion pressure

Cerebral perfusion pressure (CPP), the pressure of blood flowing to the brain, is normally fairly constant due to autoregulation, but for abnormal mean arterial pressure (MAP) or abnormal ICP the cerebral perfusion pressure is calculated by subtracting the intracranial pressure from the mean arterial pressure: CPP = MAP − ICP 

Monro-Kellie hypothesis

Monro-Kellie doctrine, or hypothesis, is that the sum of volumes of brain, CSF, and intracranial blood is constant. An increase in one should cause a decrease in one or both of the remaining two. This hypothesis has substantial theoretical implications in increased intracranial pressure and in decreased CSF volume. Many of the MRI abnormalities seen in intracranial hypotension or CSF volume depletion can be explained by the Monro-Kellie hypothesis. These abnormalities include meningeal enhancement, subdural fluid collections, engorgement of cerebral venous sinuses, prominence of the spinal epidural venous plexus, and enlargement of the pituitary gland.

Bell Magendie Law

Bell Magendie Law

In anatomy and neurophysiology, this is the finding that the anterior spinal nerve roots contain only motor fibers and posterior roots only sensory fibers and that nerve impulses are conducted in only one direction in each case.

Exception- The unmyelinated Group C nerve fibers that transmit pain and temperature from the pelvic viscera enter the spinal cord via ventral roots at L5-S3, thus violating the Bell–Magendie law.

Mc Donald Criteria 2010