aCase 20a

by Dr.Chua & Dr. Alhady
 

This 5 year-old girl was bitten by her family pet dog and sustained scalp laceration and a right red eye. The laceration was sutured in Miri General Hospital and she was seen by the local ophthalmologist who noted a right exotropia (Figure 1). She was referred to the Kuching Sarawak General Hospital for further management.

Examination confirmed the presence of a right exotropia with incomplete right adduction (Fuigure 2). Slit-lamp examination revealed laceration of the right medial conjunctiva with exposure of the tenon capsule. Her vision was normal in both eyes and fundoscopy showed no retina injuries.

Figure 1. Right exotropia and medial conjunctiva laceration.

Figure 2. Full right abduction but incomplete adduction.

An urgent MRI scan was requested to assess the status of the medial rectus. However, because of the long waiting time for MRI, a CT scan was performed instead. This showed swelling of the medial rectus near its insertion, otherwise there is no sign of medial rectus disinsertion (Figure 3 and 4).

Figure 3. Swelling of the medial rectus on CT scannings.

Figure 4. CT reconstruction showed the medial rectus is not disinserted.

a. Which extraocular muscle is commonly involved in a dog bite?

The superior oblique muscle.

 

This result from direct trauma (from the lower teeth of the dog)  to the trochlear causing paralysis of the superior oblique muscle and a Brown's syndrome due to scarring. This condition is also called dog-bite syndrome or canine tooth syndrome^1,2.

 

Perforation of the globe had also been reported and the visual prognosis is usually poor³.

b. How would you manage this patient?

As the vision is normal and the CT scan did not reveal medial rectus disinsertion, exploration with medial rectus repair was not performed. She was given topical antibiotic and steroid. The vision needs to be checked at regular interval until the eye muscle returns because of the risk of strabismic amblyopia.

 

In addition it is important to give tetanus and rabies (if it were a wild dog) prophylaxis⁴.

Reference:

1. Lee WB, O'Halloran HS. A report of canine tooth syndrome. Orbit. 2004 Mar;23(1):53-7.
 

2. Wise J, Kraus D, Goldberg LL. Dog-bite syndrome: an approach to its management. Can J Ophthalmol.

    1982 Dec;17(6):262-65.

3. Jones NP. Perforating eye injuries caused by dog bites. J R Soc Med. 1990 May;83(5):332-3.

4. Herman DC, Bartley GB, Walker RC. The treatment of animal bite injuries of the eye and ocular adnexa.
    Ophthal Plast Reconstr Surg. 1987;3(4):237-41.