Ill-conceived questions

Type of article: Letter to the Editor

Harsha Halahalli, Department of Physiology, KS Hegde Medical Academy, Mangalore, India.

Received 20 January 2008; accepted 20 January 2008.

I agree with the author [1] that, from a mechanistic point of view, little is achieved by differentiating the terms "tetanus" and "tetany". Tetany is best thought of as a clinical feature that may be seen in a variety of conditions including Clostridium tetani infections and hypocalcemia. The line of questioning that is referred to by the author does lead to the erroneous conclusion that tetany is a distinct condition that is attributable solely to hypocaclcemia. This is just one example of how ill-conceived and poorly framed questions could create flawed concepts in students. Having said this, it may however be noted that there is a difference in the pathogenesis of tetany resulting from tetanotoxin and hypocalcemia. While the site of action of tetanotoxin is pre-synaptic to the alpha-motorneurons in the spinal cord, hypocalcemia affects the motor neuronal membrane itself [2]. But the consequence of both is the increase in the firing rate of alpha-motoneurons resulting in the features of tetany.

Conflict of interests: none

References:

[1] Prakash ES. What is the difference between tetanus and tetany? Medical Physiology Online, article 3; volume 1: 2008; available from http://www.medicalphysiologyonline.org, accessed 17 January 2008

[2] Kandel ER, Schwartz JH and Jessel MT. Chapter 14: Transmitter Release; In: Principles of Neural Sciences, 4th Edn, Mc Graw Hill Co., New York, 2000.

Editor's note: I commissioned and reviewed this letter.
E.S.Prakash, Editor, Medical Physiology Online