Spasmus Nutans

From EyeWiki


Spasmus Nutans


Disease Entity

Disease

Spasmus nutans is an acquired form of nystagmus that occurs in children typically within the first 2 years of life. It presents as a clinical triad of 1) nystagmus 2) head bobbing 3) torticollis. The current theory holds among researchers that head bobbing and torticollis are compensatory mechanisms that improve vision by reducing the frequency and asymmetry of the nystagmus.

Etiology

In most cases, spasmus nutans is a benign idiopathic disorder, however studies with monozygotic twins have also revealed a possible familial component. Usually the disorder disappears by age 3 or 4. There are rare cases that spasmus nutan-like nystagmus is associated with chiasmal or suprachiasmal lesions in the brain thus warranting consideration for neuroimaging on babies with this disorder. Furthermore,  spasmus nutan-like nystagmus has also been associated with retinal dystrophies such as congenital stationary night blindness which can be confirmed by Electroretinography (ERG) and genetic testing if indicated.

Diagnosis

The diagnosis can be made if all 3 components of the triad are present. If concern for intracranial tumor or retinal dystrophy, neuroimaging and ERG can help evaluate for these potential findings.

Signs

Nystagmus is usually bilateral and characterized by high frequency, small amplitude (shimmering) nystagmus. It has also been described as monocular, asymmetric, and occasionally intermittent. Furthermore, it can be horizontal, vertical, rotatory and variable in different gaze positions. Some form of head bobbing and neck posturing is also present. Warning signs to look for that might warrant a more hasty referral for brain magnetic resonance imaging (MRI) would be any evidence of optic nerve dysfunction such as optic disc pallor or relative afferent pupillary defect. While it would be ideal to be able to determine whether a patient with nystagmus resembling spasmus nutans has associated intracranial abnormalities based on the eye and head movements alone, studies have indicated that there is no difference between the patients with spasmus nutans with and without intracranial lesions. This once again confirms that the differentiation must be made on the basis of neuroimaging.

Diagnostic procedures

As previously discussed, the diagnosis of spasmus nutans warrants consideration for neuroimaging, usually MRI, as this is generally more sensitive in revealing pathology in anterior visual pathway i.e. optic nerve glioma than computed tomography (CT) scan. In addition, MRI testing over CT scan removes the risk of radiation exposure to a growing child. Also, ERG should be considered in children with nystagmus resembling spasmus nutans and clinical signs of a retinal dystrophy such as high refractive error, poor visual function or paradoxical pupils.

Differential diagnosis

  • Spasmus nutan-like nystagmus (condition where children have nystagmus, head nodding and abnormal head position similar to spasmus nutans but symptoms are associated with low vision)
    • Optic nerve hypoplasia
    • Achromatopsia
    • Congenital stationary night blindness
    • Bardet-Biedl syndrome
  • Neurologic diseases
    • Optic pathway glioma (chiasmal)
    • Arachnoid cyst
    • Opsoclonus-myoclonus syndrome
    • Diencephalic syndrome
    • Leigh syndrome
  • Idiopathic infantile nystagmus
  • Empty sella
  • Thalamic neoplasm

Management

Aside from the aforementioned neuroimaging and ERG (as clinician deems fit), there are no other management strategies as this is a self-limited condition. Obviously, it is important to treat the underlying intracranial lesion if present and manage ocular disorders like refractive error, strabismus and amblyopia.

Prognosis

The prognosis for spasmus nutans is very good. Long term follow up studies have shown that good visual acuity can be expected in patients with spasmus nutans. However, often subclinical nystagmus persists until at least ages 5 to 12. In addition, patients with spasmus nutans have a higher incidence of amblyopia, strabismus and developmental delay.

References

  1. Basic and Clinical Sciences Course (BCSC): Pediatric Ophthalmology and Strabismus. Childhood Nystagmus, Acquired Nystagmus: Spasmus Nutans.
  2. Gottlob I, Wizov SS, Reincecke RD. Spasmus nutans. A long-term follow up. Invest Ophthalmol Vis Sci. 1995;36(13): 2768-2771.
  3. Gottlob I, Zubcov AA, Wizov SS, Reinecke RD. Head nodding is compensatory in spasmus nutans. Ophthalmology. 1992 Jul;99(7):1024-31.
  4. Gottlob I, Zubcov A, Catalano RA, Reinecke RD. Koller HP, Calhoun JH, Manley DR. Signs distinguishing spasmus nutans (with and without central nervous system lesions) from infantile nystagmus. Ophthalmology. 1990 Sep;97(9):1166-75.
  5. Yoo TK, Han SH, Han J. RP2 Rod-Cone Dystrophy Causes Spasmus Nutans-Like Nystagmus. J Neuroophthalmol. 2021 Mar 1;41(1):e91-e93. doi: 10.1097/WNO.0000000000000880. PMID: 31972715.
  6. Brodsky MC, Keating GF. Chiasmal glioma in spasmus nutans: a cautionary note. J Neuroophthalmol. 2014 Sep;34(3):274-5. doi: 10.1097/WNO.0000000000000121. PMID: 24699142.
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