The range of upward gaze is frequently restricted by extraneous factors, such as drowsiness, increased intracranial pressure, and particularly, aging. In a patient who cannot elevate the eyes voluntarily, the presence of reflex upward deviation of the eyes in response to flexion of the head (“doll’s-head maneuver”) or to voluntary forceful closure of the eyelids (Bell phenomenon) indicates that the nuclear and infranuclear mechanisms for upward gaze are intact and that the defect is supranuclear. However useful this rule may be, in some instances of disease of the peripheral neuromuscular apparatus—such as Guillain-Barré syndrome and myasthenia gravis—in which voluntary upgaze may be limited, the strong stimulus of eye closure may cause upward deviation, whereas voluntary attempts at upgaze are unsuccessful, thereby spuriously suggesting a lesion of the upper brainstem. In addition, approximately 15 percent of normal adults do not show a Bell phenomenon; in others, deviation of the eyes is paradoxically downward.
In patients who during life had shown an isolated palsy of downward gaze, autopsy has disclosed bilateral lesions of the rostral midbrain tegmentum (just medial and dorsal to the red nuclei). An unusual case, described by Bogousslavsky and colleagues, suggests that a paralysis of vertical gaze may follow a strictly unilateral infarction that comprises the posterior commissure, riMLF, and INC. Hommel and Bogousslavsky have summarized the location of strokes that cause monocular and binocular vertical gaze palsies.
Several degenerative and related processes exhibit selective or prominent upgaze or vertical gaze palsies, as mentioned earlier (Table 13-1). In progressive supranuclear palsy, a highly characteristic feature is a selective paralysis of vertical gaze, with the more specific feature being downward paralysis beginning with impairment of saccades and later, restriction of all vertical movements. Parkinson and Lewy-body diseases (see Chap. 38), corticobasal ganglionic degeneration (see Chap. 38), and Whipple disease of the brain (see Chap. 31) may also produce vertical gaze palsies as these diseases progress.
Other Supranuclear Disorders of Gaze
The ocular tilt reaction, in which skew deviation (supranuclear vertical misalignment of the eyes, discussed further on) is combined with ocular torsion and head tilt, is attributed to an imbalance of otolithic-ocular and otolithic-colic reflexes. In lesions involving the vestibular nuclei, as occurs in lateral medullary infarction, the eye is lower on the side of the lesion. With lesions of the MLF or INC, which can also cause skew and an ocular tilt reaction, the eye is higher on the side of the lesion.
Another unusual disturbance of gaze is the oculogyric crisis, or spasm, which consists of a tonic spasm of conjugate deviation of the eyes, usually upward and less frequently, laterally or downward. Recurrent attacks, sometimes associated with spasms of the neck, mouth, and tongue muscles and lasting from a few seconds to an hour or two, were pathognomonic of postencephalitic parkinsonism in the past. Now this phenomenon is observed as an acute reaction in patients being given phenothiazine and related neuroleptic drugs and in Niemann-Pick disease. The pathogenesis of these ocular spasms is not known. The drug-induced form may be terminated by the administration of an anticholinergic medication such as benztropine.