Chiari 1 Malformation presenting as “ Strabismus of obscure cause”

1. Chiari 1 Malformation presenting as “Strabismus of obscure cause” Kowal, L & Yahalom, C OMC & CERARVEEH, Melbourne

2. Chiari 1 malformation (C1M) • Tonsillar herniation ≥ 3 - 5 mm below foramen magnum • Unlike many congenital CNS malformations, C1M patients usually asymptomatic until late childhood or early adulthood

3. Symptoms & Signs of C1M • Symptoms : nonspecific - headache, dizziness, neck pain, extremity weakness, numbness …. • Neurologic signs: ataxia, dysarthria, nystagmus, cranial nerve deficit ….

4. THIS SERIES : 12 CASES • 12 cases of acquired strabismus [mostly convergent = esotropia] as the presenting sign of C1M. • No other credible explanation for the strabismus • Isolated acquired esotropia has been previously described as a rare presenting sign of C1M in several case reports - this will be the largest series so far.

5. NON- STRABISMIC FEATURES • 10/12 : ‘minor’ neurological symptoms esp. headache • 2/12 : “CHIARI PLUS” - more serious neurological signs/symptoms (#10 & #11)

6. 10 /12 patients with esotropia • 4/10 D>N ‘divergence insuff’ Some may be bilateral 6ths • 2/10 N>D ‘convergence Xs’ • 1/10 N=D • 1/10 6th nerve palsy • 2/10 ET + vertical deviation

7. 4 patients : ET D>N • All : Headache, no other neurological symptoms/signs. • All : Refraction -1.50 to +1 DS • # 9 : ET N=30, D=35 at age 7 yrs. Strab surgery planned • NSD = Neurosurgical decompression • * Range of measurements at different examinations

8. 2 patients : ET N>D # 10 : “ Chiari plus”. She has developmental delay, and early closure of fontanelles. MRI : 7 mm C1M, stable mild ventriculomegaly.

9. Other presentations • Patient #12: NSD 6 mo s/p dx of CM1. Little improvement in ET  Bimedial recession 2/04. Ortho 8 mo later • The other patients manage with glasses. • Patients #12 and #2 presented with headache as well as diplopia

10. Other presentations • # 11 is the second “Chiari plus”. His symptoms began with diplopia and balance problems. Diplopia persisted s/p 2 neurosurgical procedures. • # 3 and #8 manage well with glasses.

11. Our patients who had surgery • #10 : Squint sx with good early results (f/u 4w) • #9 : NSD. Strab persists. BMR planned. • #11 : NSD. Strab persists. Prism working. • #12 : NSD. Strab persists. Successful squint sx (f/u 8 mo). NSD: neurosurgical decompression

12. Age at presentation Most of the patients presented outside normal age range for strabismus

13. ET as only manifestation of C1MSummary of published literature *One patient from Lewis’s series did not get any sx treatment / PT= Primary treatment

14. Summary of published literature : ET as the ONLY manifestation in C1M • 16 patients ages 5 - 37 • 7/16 : strabismus sx as primary treatment • 6/7 : recurrence of strabismus • 4/5 : subsequent NSD with resolution of strab • 8 patients : NSD as primary treatment • 7/8 had resolution all signs/symptoms • Conclusion: Strab Sx alone usually ineffective. NSD usually necessary & effective.

15. Summary • We describe 12 cases of ‘acquired strabismus of obscure cause’ probably caused by C1M • 5/12 aged 10-20 @ presentation • 10/12 had headache • Esotropia was the usual squint (10/12) • 4/12 : ‘divergence insufficiency’ ET, D > N • 1/12: [apparent] sixth nerve palsy • 1/12: unexplained head tilt. • 2/12: i/mitt diplopia with poor motor fusion

16. Summary • Most patients were referred for neurosurgical evaluation. 3/12 had NSD. It is generally felt by neurosurgeons that strabismus alone is an inadequate reason for NSD. • Strabismus did not resolve in these 3 cases, with subsequent successful squint surgery in 1case. • Other patients : Most manage well with prism glasses.

17. Conclusions • Isolated acquired strabismus is not a rare presenting sign of C1M, and there might be a good number of patients being mis / under- diagnosed. • Appropriate primary management of C1M with strabismus alone [whether strabismus surgery or NSD] is unclear.