Pharmacological diagnosis of autonomic pupil denervation
Michał Fila, Andrzej Bogucki
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Pharmacological tests are widely used in evaluation of autonomic pupil denervation in Western Europe and United States. These tests allow to localize the level of lesion of pupil’s autonomic pathways. The application of such tests can reduce the number of the other necessary and expensive diagnostic tests, including imaging studies. Such approach is of special value in diagnosing sympathetic pupil denervation, due to complexity of the sympathetic pathways. The use of pharmacological test in diagnosis of pupil denervation is limited in Poland due to unavailability of the necessary substances. The lack of availability of adequate pharmacological substances is the main factor limiting this form of diagnostics. The most useful tests used in diagnostics of sympathetic pupil denervation are the hydroxyamphetamine and cocaine tests. The application of hydroxyamphetamine enables the investigator to distinguish first or second neuron damage from the third neuron injury. However, the cocaine test allows to distinguish between the first neuron damage and the injury of the second or third sympathetic neuron innervating the pupil. Thus, only application of both tests – one after the other – allows us to precisely locate the site of damage in the sympathetic pathway. Unfortunately, the cocaine solution is not available in Europe (is only used in the USA). In case of suspected damage of parasympathetic pathway innervating the pupil, the most used is the carbachol test. Unfortunately, this substance is not perfect, because after application to the eye, the pupil with damaged second parasympathetic neuron or the pupil in a patient with Holmes-Adie syndrome act exactly the same. Thus it is only possible to distinguish between the first parasympathetic neuron damage and second neuron damage or Holmes-Adie syndrome. The pilocarpine test enables the investigators to distinguish the pharmacological blockade of cholinergic receptors in synapse from all other possible causes of pathological pupil dilatation.