Thamizh selvi S., B.Optom

Aravind Fellowship in Optometry, Aravind Eye Care System, Chennai, India

Have you ever experienced tears in one eye while you are eating or chewing the food? Are you intrigued to find out the reason behind this? This blog tries to explain this bizarre phenomenon with substantial scientific evidence.

Bell’s palsy is facial nerve palsy leading to facial muscle weakness due to an unknown cause. Nemet et al.(1) found the incidence of Bell’s Palsy to be 0.08% per year and usually the incidence increases with age (fourth to sixth decades of life). In a study published by Valenca et al.,(2) females are found to be more susceptible to this especially when the left part is involved.

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The sequelae of Bell’s palsy such as synkinesis, crocodile tears Syndrome, spasm, contracture, tinnitus and/or hearing loss during facial movement were observed (3). The term “crocodile tears” is derived from the ancient belief that crocodiles weep after killing their victims. “Crocodile tears syndrome (CTS) ” also known as Bogorad syndrome and gustatory lacrimation, is the shedding of tears while eating or drinking in patients recovering from Bell’s Palsy.(4,5) CTS involves unilateral lacrimation or tearing whenever the patient is eating or drinking. CTS is a complication occurring in Bell’s palsy. As stated by Yamamoto et al., CTS occurs after approximately 6 to 9 months after Bell’s palsy. (3)

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After recovering from Bell ’s palsy, the regenerating gustatory fibres become secretory fibres to the lacrimal gland and cause homolateral tearing while eating. The anatomy of the facial nerve is a mixed nerve that has motor, sensory and parasympathetic components (superior salivatory and lacrimatory nucleus). The superior salivatory nucleus receives information from the hypothalamus and taste sensation from the oral cavity. It innervates the submaxillary and sublingual salivary glands via preganglionic fibres.(6)

The Mechanism of Lacrimation:

The lacrimatory nucleus receives information related to emotional responses from the hypothalamus. Information from the sensory nuclei of the trigeminal nerve is also received by the lacrimatory nucleus which brings about reflex lacrimation upon irritation of the cornea or conjunctiva. In the recovery period following facial nerve injury, the regenerating salivary nerve fibres undergo synkinesis or are misdirected to ultimately innervate the lacrimal gland instead of the submandibular gland. The regenerating nerves are directed toward the lacrimal gland via the greater superficial petrosal nerve (GSPN). As a result, any stimuli such as the smell or taste of food, instead of causing salivation, excites the lacrimal gland to produce ipsilateral tearing. (6)

On clinical and slit-lamp examination of the eye and the lacrimal appendages, it appears within normal limits. This rules out other causes of epiphora such as lacrimal duct obstruction, chronic dacryocystitis, punctal stenosis, conjunctivitis, and foreign body in the conjunctiva. CTS is mostly a diagnosis of exclusion in patients with a prior history of facial nerve palsy. Patients with the previous incidence of Bell’s palsy may give a history of acute-onset symptoms of neck, mastoid, or ear pain, altered taste or facial sensation, and hyperacusis.

Treatment:

The treatment of CTS depends on the severity of the hyper lacrimation and the need of the patient. Mild cases are generally managed by counselling and regular monitoring. (6)

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Several surgical options include excision of the palpebral lobe of the lacrimal gland, etc. are available. Nevertheless, these options are redundant, drastic, and have persistent side-effects such as vision loss and total ablation of the lacrimal gland. (6)

The most widely accepted treatment of crocodile tears syndrome is botulinum toxin injection into the lacrimal gland. (7) Botulinum toxin dose injected into the lacrimal gland is 2.5 units and its effect lasts for around 6 months. Montoya et al report that the injection of botulinum toxin into the lacrimal gland in crocodile tears syndrome is a safe and effective method for treating excessive tearing.

Conclusion:

Not every person with Bell’s palsy may be aware of the fact that they cry when they eat. Although it is not prevalent, yet it is important to be aware of it. Thus, patient with Bell’s palsy should be probed whether they get watering of eyes while eating and, advised to be followed up in six months period.

References:

1. Nemet, A. Y., & Vinker, S. (2015). Considerations and complications after Bells’ palsy. Journal of Clinical Neuroscience, 22 (12), 1949-1953.
2. Valença, M. M., Valença, L. P. A., & Lima, M. C. M. (2001). Idiopathic facial paralysis (Bell´ s palsy): a study of 180 patients. Arquivos de Neuro-Psiquiatria, 59(3B), 733-739.
3. .Yamamoto, E., Nishimura, H., & Hirono, Y. (1988). Occurrence of sequelae in Bell’s palsy. Acta oto-laryngologica. Supplementum, 446, 93-96.
4. McCoy, F. J., & Goodman, R. C. (1979). The crocodile tear syndrome. Plastic and reconstructive surgery, 63(1), 58-62.
5. Morais Pérez, D., Dalmau Galofre, J., Bernat Gili, A., & Ayerbe Torrero, V. (1990). Síndrome de las lágrimas de cocodrilo [Crocodile tears syndrome]. Acta otorrinolaringologica espanola, 41(3), 175-177.
6. Spiers A. S. (1970). Syndrome of “crocodile tears”. Pharmacological study of a bilateral case. The British journal of ophthalmology, 54(5), 330-334.
7. Nava-Castañeda, A., Tovilla-Canales, J. L., Boullosa, V., Tovilla-y-Pomar, J. L., Monroy-Serrano, M. H., Tapia-Guerra, V., & Garfias, Y. (2006). Duration of botulinum toxin effect in the treatment of crocodile tears. Ophthalmic plastic and reconstructive surgery, 22(6), 453-456.

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