Case Study 23: 1-year-old male with intermittent eye misalignment

HPI
A 1-year-old male presents with intermittent eye misalignment noticed by his mother several times per day. She is not sure which eye is affected. His mother also noticed that his head is constantly turned to the left. She describes tearing in the patient’s left eye when he is eating.

Past Ocular History
None

Ocular Medications
None

Past Medical History
Congenital anomalies: partial chromosome 4 deletion of unknown clinical significance, double superior vena cava, horseshoe kidney, ventricular septal defect, hypoplastic aortic arch and mitral valve, sacral dimple, L ear tag, scoliosis

Surgical History
None

Past Family Ocular History
None

Social History
Lives at home with mother, father and other brother. No smoke exposure.

Medications
None

Allergies
None

ROS
Otherwise negative

Ocular Exam

Visual Acuity (cc)
OD: CSM (central, steady, maintained)
OS: CSM

IOP (iCare tonometry)
OD:16 mmHg
OS: 12 mmHg

Pupils
Equal, round and reactive to light, no APD.

Extraocular Movements
OD: Full
OS: -3 abduction deficit

Confrontational Visual Fields
Responds to toy in four quadrants with each eye

Slit Lamp:

Lids and Lashes	Normal OU
Conjunctiva/Sclera	White and quiet OU
Cornea	Clear OU
Anterior Chamber	Deep and quiet OU
Iris	Round and reactive, normal pupil OU
Lens	Clear OU
Anterior Vitreous	Normal OU

Dilated Fundus Examination:

OD	CDR 0.2, normal optic disc, flat macula with normal foveal light reflexes, normal vessels
OS	CDR 0.2, normal optic disc, flat macula with normal foveal light reflexes, normal vessels

Sensorimotor Exam:

Retinoscopy:
OD: 2.50 +1.00 x 180
OS: 2.50 +1.00 x 180

 

Diagnosis
Type 1 Duane Syndrome of the left eye

Differential Diagnosis
This patient is presenting with Type 1 Duane Syndrome. Other diagnoses to consider are left cranial nerve 6 palsy, orbital tumor, Moebius Syndrome, Ciancia Syndrome, and congenital fibrosis of the EOM. A cranial nerve VI palsy would cause an abduction deficit, but typically a larger esotropia would be expected than seen in this patient. An orbital tumor could also cause an abduction deficit but is less likely due to other findings suggesting Duane Syndrome, including globe retraction and lid fissure narrowing on adduction. Moebius Syndrome is a congenital abnormality of cranial nerve VI and VII that can cause facial paralysis and abduction deficits. It can be unilateral but is unlikely in this case since there is no facial asymmetry or facial muscle weakness indicating cranial nerve VII involvement. Ciancia Syndrome is a congenital esotropia due to tight medial rectus muscles. It is unlikely in this case, because a much larger esotropia would be expected. Congenital fibrosis of the extraocular muscles could cause an abduction deficit, but ptosis and diffuse ophthalmoplegia would be expected and are notably absent in this patient.

Definition
Duane Syndrome is a congenital restrictive motility disorder in which the cranial nerve VI nucleus and nerve are absent or only partially developed. The lateral rectus, therefore, receives little or no innervation from cranial nerve VI. In response, other cranial nerves (particularly III) contribute innervation to the lateral rectus. There are three main types of Duane Syndrome. In Type 1 there is an abduction deficit, in Type 2 there is an adduction deficit, and in Type 3 there is both an adduction and abduction deficit. Type 1 is the most common and represents >75% of all cases. Most patients present with either a small esotropia or no misalignment. Findings indicative of Duane Syndrome include abduction and/or adduction deficit and globe retraction and lid fissure narrowing in adduction. Upshoots and downshoots in adduction are also common. Cranial nerve III innervation of the medial and lateral rectus muscles causes simultaneous contraction, resulting in globe retraction. Most commonly, the disorder is unilateral but can be bilateral in 15-20% of cases. In unilateral cases, a compensatory head turn is very common to allow binocular vision. There was a very small esotropia in this patient. His mother was noticing intermittent misalignment, which was most likely misalignment when the patient looked to the left, since his left eye has a large abduction deficit.

Duane Syndrome can be an isolated process, but it commonly has ocular and/or congenital associations. About 14% of patients develop amblyopia. Amblyopia is defined as poor vision in an eye that is otherwise normal on exam. Hyperopia is also a common ocular association. Crocodile Tears Syndrome is another association that occurs when accessory branches of the gustatory nerve innervate the lacrimal gland, which causes tearing while eating. Approximately 33% of patients have at least one associated congenital anomaly, most commonly musculoskeletal, foot, and ear anomalies. Heart and kidney defects are also common. This patient had Crocodile Tears Syndrome, as well as several congenital anomalies that are possibly associated with his Duane Syndrome and/or his chromosomal abnormality.

Examination
Duane Syndrome requires a complete and detailed ophthalmic exam with particular attention given to the sensorimotor exam. The sensorimotor exam is crucial for the evaluation of Duane Syndrome, as it can identify the cardinal features of the disorder, including eye misalignment, extraocular movement deficits, globe retraction, and lid fissure narrowing. A slit lamp exam and dilated fundus exam are important to investigate for any ocular associations that are common in Duane Syndrome, as evaluating the overall health of the eye. A multidisciplinary workup should be considered, since there are many non-ocular associations.

Treatment
The treatment for Duane Syndrome most commonly involves regular eye exams to monitor for hyperopia and amblyopia. If either develops, glasses and/or patching may be used for treatment. Surgical intervention is avoided if possible, because the innervational disorders limit the predictability of outcomes. Possible indications for surgery include persistent strabismic amblyopia, significant misalignment, marked anomalous head posture, disfiguring retraction of the globe, significant upshoots and downshoots in adduction, and for cosmetic reasons.

1. What is the primary eye movement abnormality associated with Duane Syndrome?
a. Impaired upward gaze
b. Limited horizontal eye movement, especially abduction
c. Nystagmus
d. Impaired downward gaze

2. Which cranial nerve is absent or hypoplastic in Duane Syndrome?
a. Optic nerve (CN II)
b. Oculomotor nerve (CN III)
c. Trochlear nerve (CN IV)
d. Abducens nerve (CN VI)

3. In patients with Duane Syndrome, what are the common associated ocular conditions that should be monitored for?
a. Optic nerve atrophy and iris coloboma
b. Myopia and retinal detachments
c. Hyperopia and amblyopia
d. Color vision deficit and early-onset cataract

1. What is the primary eye movement abnormality associated with Duane Syndrome?
b. Limited horizontal eye movement, especially abduction.
Horizontal eye movement is affected. Type 1 is the most common and only affects abduction. Type 2 affects only adduction. Type 3 affects both abduction and adduction.

2. Which cranial nerve is absent or hypoplastic in Duane Syndrome?
d. Abducens nerve (CN VI)
CN VI is affected. This should make sense since the most common presentation is an abduction deficit. Adduction can be affected (in Type 2 and 3) depending on how many nerve fibers abandon the medial rectus to innervate the lateral rectus.

3. In patients with Duane Syndrome, what are the common associated ocular conditions that should be monitored for?
c. Hyperopia and amblyopia
Hyperopia and amblyopia are common associations that are routinely monitored for. 14% of patients with Duane Syndrome develop amblyopia.