clonus : sign of upper motor neuron

Clonus

•      Clonus is a series of involuntary, rhythmic, muscular contractions & relaxations.

•      Clonus is a sign of certain neurological conditions, particularly associated with upper motor neuron lesions involving descending motor pathways, and in many cases is, accompanied by spasticity (another form of hyperexcitability).

•      Clonus is most commonly found at the ankle, specifically with a dorsiflexion/plantarflexion movement (up and down).

•      Some case studies have also reported clonus in the finger, toe, and laterally in the ankle (as opposed to the typical up and down motion).

•      Ankle (medial gastrocnemius)

•      Patella (knee cap)

•      Triceps surae

•      Biceps brachii

•      Causes :

•      Clonus is typically seen in people with cerebral palsy, stroke, multiple sclerosis, spinal cord damage and hepatic encephalopathy

•      Clonus has also appeared after ingesting potent serotonergic drugs, where ingestion strongly predicts imminent serotonin toxicity (serotonin syndrome). 

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Locking of the knee joint : summary

Locking of the knee joint

•      Medial rotation of the femur on tibia during terminal phase of extension (last 30° of extension )

•      It is brought about by quadriceps femoris

•      Locked knee becomes absolutely rigid

•      All ligaments are taut

•      Function: locking of the joint bring the joint into close packed

•      Clinical anatomy :

•      True Knee Locking: True locking at the knee is where the knee gets physically stuck and you physically can't move the knee for a period of time.

•      True knee locking is caused by a mechanical block where something gets caught inside the joint, preventing movement.  Cause: menisci tear , loose body

•      True locking is fairly rare and typically occurs as you move the knee into full extension, i.e. towards being fully straight.

•      Pseudo Knee Locking: Pseudo knee locking is much more common than true locking.

•      Here, knee movement is limited by temporary by muscle spasming as the body tries to protect itself in response to pain. Ex: inflammation , swelling etc

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Anatomy of Lumbar splanchnic nerve

Lumbar splanchnic nerve

It is the peripheral nerves of sympathetic nervous system

Location of preganglionic neuron : Its pre-ganglionic neurons are located in the  lateral horn of gray matter of Lumbar 1,2 spinal cord segment

Sympathetic ganglion : Its preganglionic fibres do not synapse with corresponding sympathetic ganglion . these fibres only pass through sympathetic ganglion 1,2.

Collateral ganglion : The pre-ganglionic sympathetic fiber of lumbar splanchnic nerve synapse with post ganglionic neuron located in the Inferior mesenteric ganglion

Nerve fibers convey by  lumbar splanchnic nerves : they convey two types of fibres

1.      they convey pre-ganglionic sympathetic fibres also known as general visceral efferent fibers which innervate smooth muscle cells

2.       They also convey general visceral afferent fibers which collect sensory information from  pelvic viscera and passage through the

·          inferior mesenteric ganglion,

·         sacral splanchnic nerve then

·         sympathetic and dorsal root ganglion

Plexus : they take part in the formation of inferior mesenteric plexus which is situated near the inferior mesenteric artery

They also form superior hypogastric plexus which situated near the bifurcation of abdominal

Function: Innervate pelvic viscera and vasculature

 

Anatomy of Sacral splanchnic nerve

Sacral splanchnic nerve

It is the peripheral nerves of sympathetic nervous system

Its pre-ganglionic neurons are located in the  lateral horn of gray matter of Lumbar 1,2 spinal cord segment

Pre-ganglionic fibre descend through sympathetic ganglion and leave sympathetic ganglion at the level of Sacral 1-5 . They do not synapse with sympathetic ganglion .

The pre-ganglionic sympathetic fiber of sacral splanchnic nerve synapse with post ganglionic neuron located in the Inferior mesenteric ganglion

So sacral splanchnic nerves convey pre-ganglionic sympathetic fibres also known as general visceral efferent fibres. They also convey general visceral afferent fibers which collect sensory information of pelvic viscera and passage through the inferior mesenteric ganglion sacral splanchnic nerve and sympathetic and dorsal root ganglion

They take part in the formation of  Inferior hypogastric plexus

Functions :

The inferior hypogastric plexus is a plexus of nerves that supplies the viscera of the pelvic cavity. The inferior hypogastric plexus gives rise to the prostatic plexus in males and the uterovaginal plexus in females