A  patient  was noted to have a persistent tonic conjugate  deviation of the eyes to the right. List 2 likely causes.

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College Answer

°     Irritative lesion of the left frontal lobe

°     Paralytic lesion of the right frontal lobe

°     Rt. Pontine lesion

Discussion

The college sure do love the disorders of conjugate gaze.

A right-sided lesion in Brodmann's Area 8 (right prefrontal cortex) tends to produce a tonic deviation towards the lesion. I suppose a stroke can be described as a "paralytic" lesion, although decribing stroke as "paralytic" or "apoplectic" has gone out of fashion since definitions of stroke underwent some revisions in the mid-1950s.

Alternatively, epilepsy can cause a tonic deviation of the eyes (and head), in which case the eyes will deviate away from the clearly lateralised seziure focus. I suppose, by this odd nomenclature, one could describe a clearly lateralised focus of epilepsy as an "irritative lesion".

A pontine lesion causes an interruption of ipsilateral gaze motor control, resulting in a deviation of the eyes away from the lesion, towards the intact pons and towards the hemiparetic side of the patient. Thus, a right gaze deviation could never be caused by a right pontine infarct. In this, the college answer is probably wrong.

The non-tonic version of this finding is called Prévost's sign, and is associated with hemineglect (the eyes merely "trend" towards one side).

In general, the chapter on Examination of eye movements contains some relevant persistent eye deviation syndromes and their associated observation findings  whereas the chapter on  Disorders of conjugate gaze deals more with findings on active oculomotor examination.

References

References

Berger, M. Fruhmann, et al. "Deviation of eyes and head in acute cerebral stroke."  BMC neurology 6.1 (2006): 23.

 

Kernan, J. C., et al. "Lateralizing significance of head and eye deviation in secondary generalized tonic‐clonic seizures." Neurology 43.7 (1993): 1308-1308.

 

Bassetti, Claudio, et al. "Isolated infarcts of the pons." Neurology 46.1 (1996): 165-175.