Download Bavasi, A

Skew deviation secondary to Joubert syndrome
Alexandra Bavasi, OD



Abstract: A young female with Joubert syndrome is assessed for abnormal eye movements. She
exhibits dissociated strabismus with skew deviation and torsional nystagmus. Strabismus
surgery was not recommended, but vision therapy may help improve oculomotor function.
Case history:
o Patient demographics: 6 year old Caucasian female
o Chief complaint: referred from the University of Washington for and eye movement
evaluation; left eye drifting outwards with increased frequency since starting 3-4 years
prior; control of eye turn seems to be diminishing, as her percentage of time out seems
more than 50% of the time
o Ocular/medical history:
 Ocular: (-) retinitis pigmentosa, (+) intermittent torsional nystagmus, (+)
intermittent left exotropia, (+) hypometric saccades, (+) skew deviation
 Medical: diagnosed with Joubert syndrome at the age of 7 months; initially
thought hypotonia and developmental delays were attributed to cerebral palsy,
but MRI showed “molar tooth” sign, indicating underdevelopment of cerebellar
vermis
 (-) hyperpnea, (-) liver/heart/kidney issues, (-) seizures, (+) hypotonia,
(+) developmental/speech delays, (+) ataxia/gait abnormalities
 Crawl: 18 months old; walk: 3 years old; talk: 2.5 years old
o Medications: none
o Other salient information: the patient has been evaluated at Casey Eye Institute, Seattle
Children’s Hospital, and at the National Institute of Health
Pertinent findings:
o Clinical:
 Corrected acuities: OD: 10/16; OS: 10/12.5; Lea symbols at 10 ft. Tested OS first,
OD second; patient eventually became distracted and could not achieve firm
endpoint (equal acuity of 20/40 recorded at previous exams)
 Hirschberg: OD: +0.50 mm; OS: +2.5 mm; alternates, but OD fixation preference
 Stereo: none
 Confrontation fields: FTFC OD, OS
 Pupils: PERRLA (-) APD; pupils dilated when either eye was occluded for acuities
 EOM: full, no restrictions OD, OS
 Fixations: unsteady; intermittent torsional nystagmus OU estimated to be about
10 degrees; no specific pattern
 Pursuits: unsteady, occasional switch in fixation, occasional saccadic intrusion
 Saccades: consistently hypometric with corrective saccades
 Head position: habitual left head tilt of varying degrees; noted on earlier exams
as being up to 35 degrees



Cover test:
 ~ 45^Alt XT (mostly LXT, and some variability in final magnitude)
 Dissociated vertical strabismus ~ 20%^ most consistent with skew
deviation: periodically alternated which eye was hyper; no distinct DVD
pattern
 Supine test: vertical deviation reduced by greater than 50%, consistent
with skew deviation
 Worth four dot: initially reported suppression OS, but patient able to alternately
suppress; could not perceive red and green dots at the same time, even looking
through 35 BI prism (no diplopia, no fusion)
 Synoptophore: unable to align targets to endpoint, as ocular alignment shifted
 Wet retinoscopy:
 OD: +5.75-1.00x180
 OS: +5.50-0.75x180
 Final Rx:
 OD: +4.75-1.00x180
 OS: +4.50-0.75x180
 Biomicroscopy: unremarkable; cyclotorsional nystagmus evident intermittently
in microscope
 IOP: digital normal to touch OD, OS
 Fundus exam: unremarkable: blonde fundi with no evidence of retinitis
pigmentosa, a common retinal finding associated with Joubert syndrome;
o Physical: review of systems negative with the exception of Joubert syndrome diagnosed
from molar tooth sign on MRI at age 7 months
 (+) developmental delays, (+) speech delays, (+) hypotonia, (+) mild ataxia and
wide gait
o Laboratory studies: (-) ERG at this time; consider ERG study at PUCO in coming months;
o Radiology studies: MRI at 7 months old: ordered to assess working diagnosis of cerebral
palsy; MRI revealed molar tooth sign, which is pathognomonic for Joubert syndrome,
and abnormal decussation of the superior cerebellar peduncles
o Others: (information gathered during previous exams): abdominal ultrasound, EEG, CBC,
coagulation profile, electrolytes, hepatic panel, total protein, LDH, and uric acid (all
normal/unremarkable)
Differential diagnosis:
o Primary/leading:
 Skew deviation secondary to Joubert syndrome
o Others:
 Dissociated vertical deviation (DVD)
 Trochlear nerve palsy
 Noncomitant exotropia
Diagnosis and discussion:
o Elaborate on the condition:

o
Joubert syndrome is characterized by a rare malformation of the cerebellar
vermis; on MRI, a “molar tooth sign” is evident; the cerebellar vermis is
responsible for controlling balance and coordination
 Common clinical features of Joubert syndrome:
 Tachypnea (rapid breathing)
 Generalized hypotonia
 Developmental delays
 Variable intellectual disability
 Ataxia
 Abnormal eye movements/eye alignment
 Seizures
 Abnormal physical features: polydactyly, cleft lip/palate, tongue, ocular
colobomas
 Heart/liver/kidney abnormalities
 Joubert syndrome can be inherited in an autosomal recessive pattern or it can
be sporadic
 it is considered to be a “ciliopathy,” which indicates that the cilia of cells are
dysfunctional, relating to the cell’s movement or anchoring; this may be linked
to the high incidence of organ problems in patients with Joubert syndrome
 Classic MRI presentation: hypoplasia of cerebellar vermis; increase in
depth/length of interpeduncular fossa with decrease in isthmus width;
thickening of superior cerebellar peduncles which are oriented more
perpendicularly than laterally to the brainstem; and sagittal vermian cleft
 Prognosis is typically related to the degree of vermis abnormality and CNS
involvement; however, early intervention and therapy techniques may improve
overall function of patients with Joubert syndrome
 Rarely, Joubert syndrome is associated with pigmentary retinopathy like retinitis
pigmentosa that can resemble presentation of Leber’s congenital amaurosis
Expound on the unique features:
 Skew deviation is a vertical misalignment of the visual axes caused by defective
supranuclear inputs: typically by damage to the prenuclear vestibular input to
ocularmotor nuclei
 It typically manifests after brainstem or cerebellar injury from stroke, multiple
sclerosis, cerebral palsy, or trauma
 It is usually accompanied by cyclotorsion, a tilt in the patient’s subjective
vertical, and subsequent head tilt/torticollis
 The head tilt in skew differs from that of trochlear nerve palsy: unlike
CN4 palsy where the patient tilts away from the affected eye, typically
skew patients will tilt in the same direction as the deviant eye; both
eyes will excyclorotate in the direction of the head tilt
 Supranuclear lesions (vs. peripheral lesions) do not typically cause diplopia
 Supine test: can be used to differentiate between superior oblique palsy and
skew deviation: if the vertical deviation reduces to more than half of the upright


value, then it is likely skew deviation; if the magnitude of misalignment is the
same, then it is likely a CN4 palsy
Treatment/management:
o Treatment and response to treatment:
 The patient was prescribed spectacles for full time wear to correct for her
outstanding hyperopia and mild astigmatism
 No sensory fusion evident: no reason to consider prism
 Mother interested in strabismus surgical consultation
 Result of surgical consultation: no surgery recommended due to
dissociated nature of misalignment; surgeon does not want to risk
creating a vertical misalignment when one does not truly exist; may
consider reducing the amount of exophoria, but only if the patient is
going under general anesthesia for some other purpose; otherwise,
surgery is not an option; surgeon also reassured mom that often times
skew deviation tends to slowly resolve over time and that the patient
may outgrow her misalignment tendency or at least develop more
control
 Vision therapy considered and recommended:
 Very unlikely that any amount of therapy will help to establish sensory
and motor fusion
 Monocular activities would be the focus of therapy
 Goals of potential therapy: improve monocular fixations, pursuits,
saccades; strengthen accommodation in each eye; work on
visual/perceptual tasks; work on hand/eye coordination
 Patient is to follow up in 1-2 months if VT is considered; otherwise follow up in
one year for CVE/DFE
o (Refer to research where appropriate)
o (Bibliography, literature review encouraged)
 http://www.aao.org/bcscsnippetdetail.aspx?id=daa80517-a4c1-4ef2-842e59dd8e3666ce
 http://www.ncbi.nlm.nih.gov/books/NBK1325/
 http://www.ninds.nih.gov/disorders/joubert/joubert.htm
 http://www.medscape.com/viewarticle/462135
 http://jcn.sagepub.com/content/14/9/583.short
Conclusion:
o While there is no treatment for Joubert syndrome, it is important for the optometric
physician, especially one who works often with pediatric patients, to be familiar with
Joubert syndrome among other syndromes that have ocular manifestations. Important
clinical findings and testing techniques can help to distinguish different syndromes from
others.
o Clinical pearls (take away points if indicated):
 Although intimidating, some large-magnitude ocular misalignments are unable
to be confidently corrected by strabismus surgeons; monocular vision therapy
may help to normalize eye movements and help the patients gain more control
over their eye movements