Bilateral Sixth Nerve Palsy
Suprarnuclear Paralysis of Downgaze
Upbeat Nystagmus on Upgaze
Wray, Shirley H.
Shirley H. Wray, MD, PhD, FRCP, Professor of Neurology, Harvard Medical School; Director, Unit for Neurovisual Disorders, Massachusetts General Hospital
Bilateral Sixth Nerve Palsy;
Supranuclear Paralysis of Downgaze;
Upbeat Nystagmus on Upgaze;
Supranuclear Paralysis of Downgaze Encephalopathy;
Gaze Evoked Upbeat Nystagmus;
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Diplopia and unsteadiness
This patient was known to be a chronic alcoholic. He presented with acute onset of unsteadiness walking which he attributed to double vision.
He was unable to give an accurate history and was disoriented for time and place.
Significant for impaired memory and cognitive function
Marked ataxia of gait.
Bilateral sixth nerve palsies.
Wernicke’s encephalopathy, produced by thiamin (Vitamin B1) deficiency is most commonly associated with alcoholism-related nutritional deficiency.
Wernicke’s can also be a component of many other syndromes involving nutritional compromise, for example hyperemesis gravidarum, cancer and stomach by-pass surgery.
The most common ocular abnormalities are:
2. Six cranial nerve palsy
3. Third cranial nerve palsy
4. Horizontal gaze palsy
5. Vertical gaze palsy
Cognitive examination reveals global confusion with defective immediate and recent memory.
Untreated Wernicke’s encephalopathy can progress to stupor and coma.
Treatment entails prompt parenteral thiamin administration for several days to insure repletion of tissue stores. Usually, the ocular abnormalities begin to improve within days, ataxia and confusion within weeks. Ophthalmoplegia and vertical nystagmus are generally reversible usually within one month. However, horizontal nystagmus and ataxia resolve completely in only about 40% of cases.
Unsteadiness of gait:
In Wernicke’s disease, ataxia is typically cerebellar, primarily affecting gait. In the acute stage of the disease, it may be so severe that the patient cannot stand or walk without support. Lesser degrees are characterized by a wide-based stance and a slow, uncertain, short-step gait; the mildest degrees are apparent only in tandem walking.
In contrast to the gait disorder, limb ataxia and intention tremor, elicited by heel-to-knee and finger-to-nose testing is relatively infrequent.
Gait ataxia can be aggravated by a peripheral neuropathy-related sensory ataxia.
The film of this patient was taken in 1971. It is a rare example of eye movement abnormalities in Wernicke’s encephalopathy.
The patient has:
• Esophoria OU
• Bilateral weakness of abduction due to bilateral sixth nerve palsy
• Bilateral horizontal gaze weakness with gaze evoked nystagmus
• Full upgaze with upbeat nysagmus
• Supranuclear paralysis of downgaze
• Absent convergence
Brain MRI demonstrates the acute lesions of Wernicke’s disease, both the medial thalamic and periaqueductal lesions. Normal findings on MR imaging do not, however, exclude this diagnosis.
The changes are most apparent on the FLAIR and T2-weighted images, but also on diffusion-weighted sequences; the latter is worthy of emphasis because changes of Wernicke’s disease may be mistaken for infarction on these images.
Imaging is particularly useful in patients in whom stupor or coma has supervened or in whom ocular and ataxic signs are subtle.
With immediate treatment and clinical improvement the imaging changes are reversible.
Bilateral medial thalamic, periaqueductal and dorsal medulla are selected anatomical sights.
Patients who die in the acute stages of Wernicke’s disease show symmetrical lesions in the paraventricular regions of the thalamus and hyperthalamus, mammillary bodies, periaqueductal region of the midbrain, floor of the 4th ventricle (particularly in the regions of the dorsal and motor nuclei of the vagus and vestibular nuclei) and superior cerebellar vermis.
Lesions are consistently found in the mammillary bodies and less consistency in the other areas.
Microscopic changes are characterized by varying degrees of necrosis of parenchymal structures. Within the area of necrosis, nerve cells are lost, but usually some remain; some of these are damaged but others are intact. Myelinated fibers are more affected than neurons.
Discreet hemorrhages are found in only 20% of cases. The cerebellar changes consist of a degeneration of all layers of the cortex, particularly of the Purkinje cells; usually this lesion is confined to the superior parts of the vermis, but in advanced cases the cortex of the most anterior parts of the anterior lobes is involved as well.
The nystagmus is attributed to lesions in the region of the vestibular nuclei, and abduction weakness to lesions of the sixth nerve nuclei. The lack of significant destruction of nerve cells in these lesions accounts for the rapid improvement and the high degree of recovery of oculomotor and vestibular functions with treatment.
Chronic alcoholism and nutritional deficiency.
Wernicke’s disease constitutes a medical emergency; its recognition (or even the suspicion of its presence) demands the immediate administration of thiamine.
The prompt use of thiamine prevents progression of the disease and reverses those lesions that have not yet progressed to the point of fixed structural change.
As emphasized earlier, in patients who show any ocular signs and ataxia, the administration of thiamine is crucial in preventing the development of an irreversible amnesic state.
Although 2 to 3 mg of thiamine may be sufficient to modify the ocular signs, much larger doses are needed to sustain improvement and replenish the depleted thiamine stores – 50 mg intravenously and 50 mg intramuscularly – the latter dose being repeated each day until the patient resumes a normal diet.
It is also advisable to give B-vitamins to patients with a history of alcoholism. The further management of Wernicke’s disease involves the use of a balanced diet and all the B-vitamins since the patient is usually deficient in more than thiamine alone.