Pupillary abnormalities and areflexia

When pupillary disorders are detected in a patient in the form of changes in the width, shape of the pupils, their response to light and to convergence with accommodation in combination with the loss of deep reflexes from the extremities (at least the Achilles reflexes), neurosyphilis is usually suspected. However, there are at least four other pathological conditions that should be kept in mind in the presence of this clinical picture.

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The main causes of pupillary disorders:

1. Eddie's syndrome.
2. Tabes dorsalis.
3. Diabetic polyneuropathy.
4. Combined degeneration of the spinal cord (funicular myelosis).

Eddie's syndrome

Complete Eddie syndrome includes: moderate pupillary dilation with almost complete absence of reaction to light or to accommodation with convergence and absence of Achilles reflexes. Sometimes knee reflexes are also absent, in rare cases complete areflexia is observed. There are no sensory disturbances, conduction velocities along the motor and sensory nerves are not changed. The patient complains of blinding effect of bright light (sun) and blurriness of the image when examining small objects at close range. On examination, absence of phasic constriction of the pupils is revealed when they are directly illuminated and during convergence with accommodation. Pharmacological test is necessary to confirm parasympathetic denervation hypersensitivity of the involved muscle (muscle that constricts the pupil).

There is some controversy as to whether this condition should be called a disease. Apart from the symptoms described above, the condition does not cause any harm to the patient, and there are no other symptoms or morbid manifestations. Edie syndrome does not require treatment, except for the recommendation to wear sunglasses.

Partial variants of Edie syndrome have been described (pupillary disorders without areflexia; areflexia without pupillary disorders). Hereditary forms of Edie syndrome are also encountered.

To exclude neurosyphilis, negative results of a serological blood test are sufficient.

Tabes dorsalis

In tabes dorsalis, the affected pupil is reduced in diameter and has an irregular shape. With a complete absence of the reaction of this pupil to light, the reactions to accommodation and convergence are completely preserved (Argil-Robertson pupil). Another difference from Edie's syndrome is the involvement, as a rule, of both eyes at once. Areflexia is combined with a variety of disorders in the sensory sphere - from a violation of deep sensitivity and the sense of posture, manifested in the form of dynamic sensory ataxia (increased ataxia when walking without visual control), to a violation of vibration and pain sensitivity. Pain stimuli are often perceived with a significant delay. The speed of conduction along the nerves is not changed.

Diabetic polyneuropathy

The most common form of peripheral nerve pathology is diabetic polyneuropathy. The absence of Achilles reflexes and decreased vibration sensitivity - even in patients who do not complain of any motor or sensory dysfunction - is a very common phenomenon. The autonomic nervous system is often involved; a clinical sign of its impairment is often constriction of the pupils and their slow, incomplete response to light and accommodation with convergence, which distinguishes these pupillary disorders from the Argyle-Robertson symptom. Deviations are always detected in the study of nerve conduction velocities - a decrease in the conduction velocity in motor and (or) sensory fibers. The degree of expression of possible deviations in the study of evoked potentials is determined by the degree of involvement of the peripheral nerves.

Combined degeneration of the spinal cord (funicular myelosis)

Of greatest interest in the context of this chapter are the 50% of patients with vitamin B12 deficiency who do not have Achilles reflexes. The characteristic complaints are paresthesias and disturbances of those types of sensation mediated by the posterior columns of the spinal cord.

Often there is a constriction of both pupils with preservation of their photoreactions. When studying the speed of conduction along the nerves, a slowdown in the conduction of excitation along the motor and sensory fibers is revealed. The degree of expression of deviations revealed during the registration of somatosensory evoked potentials and reflecting the interest of the posterior columns significantly exceeds that which could be attributed to the involvement of peripheral nerves. This, in particular, also applies to evoked potentials from the anterior tibial and sural nerves. Naturally, serological tests for the presence of syphilitic infection are negative.

The diagnosis is not difficult when there are signs of paresis of the extensors of the foot; this is observed in about 50% of cases. It is clear that for a positive diagnosis it is necessary to prove a violation of the absorption of vitamin B12 in the intestine.