Lacrimation and the act of micturition are both under the control of the parasympathetic nervous system. Despite being so similar in their control they never go together except if emotion is attached, like pain. Lacrimation associated with painless act of micturition has been earlier mentioned in few case reports [1-3]. Here we report a young girl with this finding.

A 5-year-old girl visited the outpatient pediatric clinic in June, 2019 with complaint of tearing from both eyes during micturition, without any associated pain or discomfort. This phenomenon was witnessed by the treating doctors also. The child was delivered at full term and had achieved all milestones at appropriate age including bowel-bladder control. There was no history of a similar phenomenon occurring in near or distant family members. The examination of the external genitalia and eyes was normal. Urine analysis and ultrasound of the urinary tract were also normal. This abnormal lacrimation got resolved with injection atropine (0.25 mg intravenous bolus just before the act of micturition).
The child was advised to pass urine frequently without the urge of micturition. Lesser amount of bladder stimulation decreased the parasympathetic activity and tearing. With this bladder regime, she reported a decrease in the tearing. The parents were counseled about the benign nature of this phenomenon as it probably represented an abnormal neural connection.

Tears relate to emotions as disparate as pain, sadness, anger, frustration, happiness, and religious aspiration. Tears may be rarely attributed to a neurological disorder or disease like the syndrome of crocodile tears. In the index case, tears were linked to urination without any emotional connection.

The central nervous control of micturition is a complex arrangement between the higher centers, the pons and the spinal cord [4]. The Pontine micturition center (PMC) acts as a switch in the micturition reflex pathway and co-ordinates the activity of the bladder and the urethral sphincter [5]. This center receives input from a higher center situated in the medial pre-frontal cortex (mPFC). The supra-spinal control of bladder and orchestration of micturition is also done by the central-autonomic-network (CAN) [6]. Like the PMC, the function of the lacrimal nuclei is also modulated by the higher centers namely the limbic system and/or CAN (medial pre-frontal cortex is a part of CAN) which controls the emotional tearing, and the trigeminal nucleus which controls the reflex tearing. No direct connection between PMC and the lacrimal nucleus (LN) has been documented till date to explain involuntary/non-emotional tearing in association with the act of micturition.

Buwler, et al. [1] hypothesized that abnormal parasympathetic connections occur between the lacrimal nucleus and the PMC which are responsible for this finding. We offer two hypotheses as the neuro-physiological basis of this phenomenon. First, it is possible that some of the mPFC neurons which were destined to synapse with the PMC inadvertently synapsed with the lacrimal nucleus leading to reflex co-activation as both receive input from the medial pre-frontal cortex. Second, lacrimal reflex and micturition reflex are both controlled by autonomic parasympathetic system which can lead to simultaneous neuronal discharges. However, in the absence of functional images, no conclusion could be drawn.

Clinicians should be aware of this phenomenon, its benign nature, and that it is at best a aberrancy and not a disease.

Contributors: MM: case management and preparation of the draft; SR: manuscript drafting and revision. Both authors approved the final manuscript as submitted and agree to be accountable for all aspects of the work.

Funding: None; Competing interest: None stated.

REFERENCES

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