A possible association with deletion of the gene GPC1, which encodes a glypican 1-a heparan sulfate proteoglycan, has been reported. This gene is located on the long arm of chromosome 2 (2q37) and is involved in the regulation of inflammation and the Hedgehog gene.Egyptian infants with biliary atresia were found to have null GSTM1 genotype while all their mothers were heterozygous for GSTM1. Thus these infants may be protected in utero by their maternal detoxification system, yet once born they cannot handle the detoxification of an aflatoxin load. Toxins
Some cases of biliary atresia may result from exposure to aflatoxin B1, and to a lesser extent aflatoxin B2 during late pregnancy. Intact maternal detoxification protects baby during intrauterine life, yet after delivery, the baby struggles with the aflatoxin in its blood and liver. Moreover, the baby feeds aflatoxin M1 from its mom, as aflatoxin M1 is the detoxification product of aflatoxin B1. It is a milder toxin that causes cholangitis in the baby.There are isolated examples of biliary atresia in animals. For instance, lambs born to sheep grazing on land contaminated with a weed (Red Crumbweed) developed biliary atresia at certain times. The plants were later found to contain a toxin, now called biliatresone Studies are ongoing to determine whether there is a link between human cases of biliary atresia and toxins such as biliatresone. There are some indications that a metabolite of certain human gut bacteria may be similar to biliatresone.
Orbital floor fractures may trap the orbital tissue in such a way as to simulate Browns syndrome. Intermittent forms of vertical retraction syndrome have been associated with click, which occurs as the restriction is released (superior oblique click syndrome). Diagnosis
Diagnosis of Browns syndrome usually happens during a routine ophthalmologic appointment. Treatments
If binocular vision is present and head position is correct, treatment is not obligatory. Treatment is required for: visual symptoms, strabismus, or incorrect head position.Acquired cases that have active inflammation of the superior oblique tendon may benefit from local corticosteroid injections in the region of the trochlea. 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 without 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.During surgery, a traction test is repeated until the eye rotations are free and the eye is anchored in an elevated adducted position for about two weeks after the surgery. This maneuver is intended to prevent the reformation of scar tissue in the same places. Normalization of head position may occur but restoration of full motility is seldom achieved. A second procedure may be required.