Definition - Clinical characteristics include the following three signs:
2) Head Nodding
3) Nystagmus - usually unilateral
|The nystagmus is:
* Usually horizontal
* Can be vertical
* Can be rotary
* Can be mixed
* Usually rapid
* Usually low amplitude
* Can be bilateral but unequal
* Of the three signs, 1) nystagmus is the most important - you cannot make the diagnosis without it, 2) head nodding is the most likely to be absent, and 3) torticollis is the least impressive.
* The age range for spasmus nutans is 6 months to approximately 3 years old.
* The cause is unknown - actually to be truly spasmus nutans the condition should be both harmless and self-limiting, and of unknown etiology (idiopathic).
* Some types of central nervous system disease can result in acquired, primarily unilateral nystagmus which mimics spasmus nutans. Leading to the question: should the patient with the signs of spasmus nutans be "worked up" and if so, how?
Since true spasmus nutans is benign and self-limiting, the answer to the above should be no!!
However, if a patient with primarily unilateral nystagmus is suspected of having spasmus nutans, but you cannot be sure that the patient does not actually have CNS disease as a cause of the nystagmus, a work up, usually consisting of a head CT scan or MRI should be done. If neuroblastoma is suspected, an abdominal CT scan should be done along with a urine test for catacholamines.
Experts are divided on whether to obtain special studies on all patients with a spasmus-nutans-like picture.
In general younger clinicians, those whose careers are entirely in the CT scan, MRI era of medicine, and those who have been unpleasantly surprised by a serious diagnosis in a patient with spasmus-nutans-like picture are more likely to obtain imaging studies.
Some serious CNS conditions that have been diagnosed in patients with spasmus-nutans-like finding are the following:
1. Chiasmal glioma
2. Nonspecific CNS degenerative disease
3. Achromatopsia - congenital stationary night blindness
4. Third ventricle tumor
Imaging should be done if a patient with spasmus-nutans-like finding has one or more of the following:
1) afferent pupillary defect
2) optic atrophy
3) failure to thrive
4) or seem to have some suggestion of any type of neurologic disease
Spasmus nutans should be differentiated from latent nystagmus which is a unilateral nystagmus occurring when the fellow eye is occluded.
Chin down null
Chin up null
When a child demonstrates congenital or acquired nystagmus which has a null or nearly null in the chin up or chin down position, serious CNS disease should be ruled out. Down beating nystagmus with chin down and upbeating nystagmus with chin up can be signs of posterior fossa lesions. Convergence - retraction nystagmus is seen with dorsal midbrain syndrome (Parinaud's syndrome). Other "nystagmoid" eye movement could also be considered indication for obtaining imaging of the head. Acquired childhood nystagmus is always a concern!
In the final analysis, the clinician must weigh each case of childhood nystagmus including spasmus nutans on its own merits and employ a conscientious, careful and systematic clinical approach.
Two Points of View
Imaging in cases of spasmus-nutans-like picture is done selectively. The management is tailored to each patient's specific needs and includes careful follow up, which includes accurate monitoring by the family. Studies may be done on the basis of the patient's unique clinical picture. A spasmus nutans "plus" clinical picture always requires investigation; plus means any other important clinical neurological sign such as optic atrophy, afferent pupil defect,etc.
If a patient demonstrates spasmus nutans, regardless of an otherwise healthy appearance, an MRI of the head is done. In most cases where spasmus nutans is the only sign the study will be normal. But, no one will praise you for saving the health care system the cost of an MRI and you will be found wanting if an MRI was not done and significant other disease is present.
The Strabismus Minute, Vol.1, No. 13 Copyright (C) 1999 Eugene M. Helveston All Rights Reserved
Editor-in-Chief: Eugene M. Helveston, M.D.
Associate Editor: Faruk H. Orge, M.D.
Editorial Board: Bradley C. Black, M.D.
Edward O'Malley, M.D.
David A. Plager, M.D.
Derek T. Sprunger, M.D.
Daniel E. Neely, M.D.
Naval Sondhi, M.D.
Senior Editorial Consultant: Gunter K. von Noorden, M.D.
Graphics: Michelle L. Harmon
Technical Support: George J. Sheplock, M.D.