What is Brown Syndrome?

Brown syndrome (BS) is a rare ocular motility disorder characterized by a limitation of elevation in adduction of the eye.  Patients with BS can have a widening of the palpebral fissure in adduction, divergence in upgaze, and hypotropia in primary position, in addition to the limitation of elevation in adduction (LEA).

Anomalies of the superior oblique (SO) tendon or the trochlea, inflammatory disorders, infection, and trauma are all possible causes of BS. The main surgical solution for this condition is the lengthening/weakening of the superior oblique muscle.

Image Credit: EJ Nickerson/Shutterstock.com

History

In 1949, Dr. Harold Brown described eight cases of a new ocular motility disease that had restricted elevation in adduction and other symptoms. Although there was modest superior oblique muscle overactivity, the clinical characteristics were similar to those of an inferior oblique palsy. Brown identified a shorter superior oblique tendon sheath during surgery, which was expected to limit passive elevating movement in the adducted field.

As a result, the term "superior oblique tendon sheath syndrome" was coined. A V or Y pattern strabismus, divergence in upgaze, downdrift in adduction, and a positive forced duction test for ocular elevation in the nasal field were discovered to be significant clinical findings after the additional examination.

Brown syndrome terminology has changed over time and might be misleading. True Brown syndrome is caused by a tight superior oblique tendon, which results in a persistent limitation of elevation and a positive traction test. Pseudo-Brown syndrome includes both chronic and episodic cases, as well as those that aren't caused by superior oblique muscle-tendon disease.

Causes and Symptoms

Brown syndrome is thought to be caused by a malfunction of the superior oblique tendon-trochlear complex. Primary congenital and acquired causes are usually used to categorize the disorder. Although many distinct causes have been identified, acquired instances can be classed as inflammatory, traumatic, or iatrogenic. Anomalies of the superior oblique (SO) tendon or the trochlea, inflammatory disorders such as rheumatoid arthritis and systemic lupus erythematosus, infection, trauma, malignancy, and iatrogenic procedures are all possible causes.

A limited rise in adduction is the hallmark sign. A down shoot in the adduction of the afflicted eye (s) might also be seen if there is a severe limitation. The positive forced duction test can confirm the diagnosis. Hypotropia can occur in the primary position and is often proportionate to the severity of the limitation. Binocular fusion and comfortable vision can be achieved by adopting an atypical head posture that includes a chin up and a contralateral face turn to avoid hypotropia.

Patients with Brown syndrome, especially those who develop it later in life, are more likely to experience diplopia when they are tropic. Systemic symptoms, such as superonasal orbital pain and sensitivity to movement or touch, can also be present in the acquired Brown syndrome of inflammatory cause. There is an audible "click" on the ocular movement.

Different forms

The severity of Brown syndrome can be graded as mild, moderate, and severe. The mild form involves restricted elevation in adduction, no hypotropia or down shoot in adduction while in the moderate form, restricted elevation and down shoot in adduction is observed along with no hypotropia in the primary position.  The severe form of BS involves restricted elevation and marked down shoot in adduction. In this case, hypotropia is present in the primary position.

Inheritance and association with other conditions

Although Brown syndrome is usually sporadic, there have been several reports of the familial Brown syndrome, notably in identical twins. Brown syndrome is usually unilateral, while 10% of instances are bilateral. Congenital SOP (superior oblique paresis) and congenital Brown syndrome may be the same condition. The superior oblique muscle is underdeveloped and the trochlear nerve is missing in both illnesses, according to imaging studies.

Tendon abnormalities are common in congenital superior oblique palsy, and the tendon in Brown syndrome is aberrant by definition. Both SOP and Brown syndrome have similar percentages of bilaterality. Both are sporadic, however, there are some examples of familial presentation. Both illnesses have been encountered in conjunction with other innervation abnormalities like CFEOM, Duane, and ptosis.

Epidemiology

Brown syndrome, according to Raynor and Hiatt in the 1970s, occurs in 1 in 450 cases of strabismus. When it comes to vertical muscle anomalies, the rate of occurrence rises. A researcher discovered 23 people with Brown syndrome among a total of 226 patients with vertical muscle paresis, all of whom had positive traction tests, according to a report.

According to several studies, Brown syndrome is more common in women, with 10% of cases showing bilaterality. Duane syndrome, crocodile tears, congenital ptosis, and Marcus Gunn syndrome have all been linked to Brown syndrome.

Diagnosis and Treatment

Following a thorough history, a thorough examination of ocular mobility should be part of the clinical evaluation. The etiology of Brown syndrome determines the evaluation and management techniques based on the patient's history and certain physical findings. Further imaging or laboratory investigations, depending on the etiology, may be required, such as radiological imaging in cases of traumatic Brown syndrome and referral to medical teams for management of inflammatory causes.

In terms of BS care, mild and moderate instances can be watched for spontaneous resolution, but the healing phase can be lengthy. In severe circumstances, surgery may be required. The mainstay of treatment for most cases of Brown syndrome is observation and conservative care. In acquired cases, spontaneous improvement is prevalent; however, it is less common in congenital cases.

Eye exercises and treatment of underlying reasons, such as oral or local injections of corticosteroids for inflammation, are non-surgical options. In sporadic cases with Brown syndrome unresponsive to steroids or nonsteroidal anti-inflammatory medication therapy, steroid-sparing immunosuppressants, such as adalimumab, have been used successfully.

Surgical surgery is recommended for patients with vertical deviation in the primary gaze position, AHP, severe diplopia, or disfiguring down shoot in adduction. SO tenectomy, SO tenotomy, Z tenotomy, split tendon lengthening, and tendon lengthening using the silicone band, adjustable nonabsorbable sutures, or autogenous expanders have all been introduced as surgical techniques for BS therapy. 

References:

• Prestinary R., Casiano R. (2022). Brown Syndrome Following Endoscopic Modified Lothrop Procedure. In: Chandra R.K., Welch K.C. (eds) Lessons Learned from Rhinologic Procedure Complications. Springer, Cham. https://doi.org/10.1007/978-3-030-75323-8_8
• Ozsoy, E., Gunduz, A., Firat, I. T., & Firat, M. (2021). Brown syndrome: clinical features and results of superior oblique tenotomy. Arquivos brasileiros de oftalmologia, 84(2), 133–139. https://doi.org/10.5935/0004-2749.20210021
• Fu L, Malik J. Brown Syndrome. [Updated 2021 Sep 28]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK563210/
• Kim, J.H., Hwang, JM. Magnetic resonance imaging in congenital Brown syndrome. Graefes Arch Clin Exp Ophthalmol 253, 1385–1389 (2015). https://doi.org/10.1007/s00417-015-2962-x
• Coussens, T., & Ellis, F. J. (2015). Considerations on the etiology of congenital Brown syndrome. Current opinion in ophthalmology, 26(5), 357–361. https://doi.org/10.1097/ICU.0000000000000191

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Written by

Emily Henderson

During her time at AZoNetwork, Emily has interviewed over 200 leading experts in all areas of science and healthcare including the World Health Organization and the United Nations. She loves being at the forefront of exciting new research and sharing science stories with thought leaders all over the world.