Saturday, 18 November 2017

Hyperactive reflexes and Clonus

Two of the HSP symptoms which are mentioned reasonably often are hyperactive reflexes and clonus, but I wasnt sure what they are, so it was time to do some investigation. And, actually its quite tricky to work out. It appears that hyperactive reflexes and clonus are related - both are grouped together under the heading Hyperreflexia. It is very easy to find plenty of references to these as being symptoms of something else. Apologies for a very link heavy post!

Looking at HSP, I find: spasticity is an increase in muscle tone with resulting stiffness. Muscle tone refers to the mild contraction that muscles continue to exhibit even when at rest (ie, resting muscle tone). A reflex between nerve endings in the muscle and spinal cord regulates muscle tone. Normally, the corticospinal nerves control and reduce sensitivity of this reflex. Because HSP causes deterioration of the corticospinal nerves, the reflex is not reduced as it should be, the result being an exaggerated (ie, hyperactive) reflex and increased muscle tone. Essentially, HSP prevents the muscles from relaxing properly.

Clonus is relatively easy to trackdown - it is alternate involuntary muscular contraction and relaxation in rapid succession. This can also be described as rhythmic. Clonus is a larger motion than a twitch, and the muscles will contract and relax between 3 adn 8 times a second, for between a few seconds and a few minutes. The connection is that these are often caused by a reflex. gives some info.  Once more there are videos of this, for example on the ankle: and a faster one here, and for the legs and here You can also see plenty of people with their legs shaking - Here's a description: This all reminds me of things I was told back in my 2013 survey about people being misdiagnosed with restless leg syndrome.

Hyperactive reflexes are more tricky to track down, and it is difficult to know what level of reflex is considered normal (although there is a scale of 0 to 4 with 2 being normal If a reflex is hyperactive then the muscles have a larger movement than normal when they are tested on the reflexes (and the score would be more than 2). You can see that some people have both hyperactive reflexes and clonus: and

There are plenty of websites and medical papers which describe people with HSP who have either or both hyperactive reflexes and clonus, but these papers tend to assume that the reader knows what they are!

(p.s. I had previously looked up clonus myself in 2012, reflecting on my jumping legs back at school:, and borrowing the clonus text from the SP Foundation website)

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