Brown-Séquard syndrome (Year of the Zebra)

[Music] Brown sard syndrome first described by the physiologist Charles Edward Brown squard is a condition associated with hemisection or damage to one half of the spinal cord the hemi-section damages neural tracts in the spinal cord that carries information to and from the brain this results in the loss of Sensations like pain temperature touch as well as paralysis or loss of muscle function in some part to the body now if you look at the cross-section of the spinal cord the white matter is on the outside and the gray matter is on the inside and overall it looks kind of like a butterfly if we draw a horizontal line through the spinal cord the front half is the anterior or ventral half and the back half is the posterior or dorsal half and the Butterfly Wings are sometimes referred to as horns so we have two dorsal horns that contain cell bodies of sensory neurons and two ventral horns that contain cell bodies of motor neurons the white matter consists of myelinated axons which are separated into tracks that carry information to and from the brain think of them like highways for neural signals where some highways carry sensory information to the brain and some carry motor information from the brain to the muscles there are a few main tracks to remember first there's the spinothalamic tract which is an ascending pathway and it's divided into two parts the lateral tract carries sensory information for pain and temperature while the anterior tract carries information for pressure and crude touch or the sense one has been touched without being able to localize where they were touched second there are two ascending dorsal column tracts the fasiculus gracilis which carries sensory information from the lower trunk and legs and the fulus catus which carries sensory information from the upper trunk and arms these tracks both carry Sensations like vibration fine touch which is where you can localize where you were touched and proprioception which is an awareness of your body position in space finally there's the corticospinal tract which is a descending pathway that carries motor information from the brain to different muscles in the body and it controls voluntary muscle movement so sensory information has to go through three neurons to reach the brain kind of like three people in a relay race for example if you accidentally touch a hot pan the sensation of pain and temperature is carried from the nerves in the skin of your fingers through a first order neuron which is a pseudo unipolar Neuron a pseudo unipolar neuron has a cell body from which only one axon comes out and then that axon splits into two branches a lateral branch that comes from the periphery and a medial branch that runs towards the spinal cord so the nerve in the skin of your fingers is served by the lateral branch of a first order neuron which carries the sensation to the dorsal root gangon that's where the cell body is located along with the rest of the cell bodies of the pseudo unipolar neurons from there the signal continues through the medial branch and into the spinal cord to reach the dorsal horn here it passes off the sensory information baton by synapsing with a second order neuron which sends off its own axon which ascends one or two spinal segments and Crosses over to the opposite side to travel up the spinal cord and eventually synapse with a third order neuron located in the ventral posterior nucleus of the thalamus this third order neuron then sends its axon up to the sensory cortex of the brain letting you know that there's tissue damage similarly if you suddenly grab a vibrating cell phone the sensation of vibration is carried from the nerves in the skin of your palm via the fasiculus catus which is a collection of nerves all composed of first order neurons the fasiculus catus is contained within the dorsal white column located posteriorly in the white matter of the spinal cord the first order neuron then ascends up along the same side of the whole length of the spinal cord to reach the lower level of the Medela oblongata where it synapses with the cell body of a second order neuron in the nucleus catus the second order neuron then sends off an axon that crosses over to the opposite side of the Medela and travels up to the ventral posterior nucleus of the thalamus to synapse with a third order neuron the third order neuron then sends up an axon that carries the sensory signals to the primary somato sensory cortex of the brain letting you know that your phone is vibrating once your brain receives sensory information it sends a motor signal down the upper motor neurons through the corticospinal tract in the midbrain and Crosses to the opposite side at the Medela before continuing down the spinal cord there they synapse with lower motor neurons in the ventral horn and the lower motor neuron axons then leave the spinal cord to innervate the muscles of your arm and forearm which allows you to lift your fingers and hand from the hot pan or pick up your cell phone hopefully this all happened quickly so you haven't sustained major tissue damage and that collar hasn't hung up in brown sequart syndrome a vertebral bone fracture or any kind of penetrating trauma like a gun sh injury or stab wound in the back can lead to the Hem section of the spinal cord and this mostly happens in the neck or cervical region besides trauma non-traumatic conditions like a spinal cord tumor might compress the spinal cord and lead to Brown seard syndrome okay so suppose a person was stabbed in the neck and had a complete right hemisection of the spinal cord this means that all the principal neural tracts in the right side of the spinal cord are now damaged damage to the right sided cortical spinal tract means that below the level of the lesion the lower motor neurons like those going to the legs are no longer receiving signals from the upper motor neuron so the muscles they control become paralyzed and this is called an ipsilateral hemiplegia or Paralysis on the same side interestingly these neurons become so starred for stimulation they become hyper sensitive and start firing inappropriately causing increased muscle tone and muscle spasms so we call this paralysis meanwhile at the level of the lesion the lower motor neuron of the right ventral horn will also be damaged this means that the muscles inated by these lower motor neurons like those in the arms will not receive any neuro input at all so they go limp and decrease in tone which is called flaccid paralysis similarly there's damage to the dorsal column on the right side which will lead to the loss of fine touch vibration and proprioception in the right side of the body at the level of the injury and below it now the spinal thalamic tract is a bit different because it crosses over to the opposite side of the spinal cord one or two spinal segments above where the first order neurons enter so it damage to the right spino thalmic tract will cause loss of pain pressure temperature and crude touch Sensation from the opposite or left side beginning one or two segments below the lesion but at the level of the lesion the spinothalamic tract of the same right side will be damaged too this will lead to complete loss of all cutaneous sensation at the level of the lesion besides those three tracts very rarely a hemisection of the spinal cord above the T1 spinal level can also damage the sympathetic chain that runs alongside the spinal cord and supplies the facial region this leads to Herer syndrome on the same side of the face as the lesion which includes symptoms of my iosis or constricted pupil tosis or droopy eyelid and anhydrosis or failure to sweat now in clinical scenarios a complete right side or complete left side hemisection is pretty rare that's why most of the time individuals with brown sequart syndrome will only present with an incomplete hemisection and some sensory or Motor problems depending on which tracks are damaged for example if an individual has been stabbed in the back and has no pain temperature sensation on the left side but normal motor function and normal fine touch and vibration it means that there's only damage to the spino thalmic tract of the right side finally magnetic resonance imaging or an MRI can be used to confirm any lesion on or within the spinal cord the treatment for brown squart syndrome is mainly supportive and focused on Rehabilitation with physical and occupational therapy typically cord swelling and inflammation can be managed with corticosteroids all right as a quick recap Bron sard syndrome is a condition associated with hemisection of the spinal cord which usually damages descending cortical spinal tracts ascending dorsal column tracts and spinal thalamic tracts the result is paralysis and loss of proprioception on the same side as the injury or lesion and loss of pain and temperature sensation on the opposite side of the leion helping current and future clinicians Focus learn retain and Thrive learn more

Channel: Osmosis from Elsevier

Views: 24,414

Keywords: Health (Industry), Medicine (Field of Study), Disease (Cause of Death), Osmosis, Pathology (Medical Specialty), what is, nursing (field of study), Nursing school (organization)

Id: 65XRCVkXcS4

Length: 10min 2sec (602 seconds)

Published: Sun Nov 05 2023