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Showing posts with label reflex. Show all posts
Showing posts with label reflex. Show all posts

Snout Reflex -clinical significance

Method of elicitation
Keep a finger on the upper lip and  a  direct tap on the lips with the examiner's finger lightly over it.
Puckering and protrusion of the lips is seen.
pressure of the knuckle against the center of upper lip provokes con-traction of the orbicularis oris muscle
This is also seen in B/l UMN facial palsy and diffuse cerebral damage.

How to elicit Palatal reflex?

Ask the subject to open his mouth widely and then touch the mucous membrane covering the palate using a spatula. This produces reflex contraction of the palatal muscles which results in sudden elevation of the palate.
  • Receptors : Touch receptors of the palatal mucosa
  • Afferent limb : Glossopharyngeal nerve and Trigeminal nerve
  • Centre : Vagus nucleus in the medulla
  • Efferent limb : Vagusnerve
  • Effector : Palatal muscle

How to elicit Corneal reflex?

The corneal reflex, also known as the blink reflex, is an involuntary blinking of the eyelids elicited by stimulation of the cornea. The purpose of this reflex is to protect the eyes from foreign bodies and bright lights (the latter known as the optical reflex)
The edge of  cornea  (limbus) is touched with  a  wisp of cotton, with the patient looking upward  in the opposite direction
  • The nasociliary branch of the ophthalmic branch (V1) of the 5th cranial nerve (trigeminal nerve) sensing the stimulus on the cornea(afferent fiber).
  • The temporal and zygomatic branches of the 7th cranial nerve (Facial nerve) initiating the motor response (efferent fiber).
  • The centre (nucleus) in the pons of brain stem.
  • Use of contact lenses may diminish or abolish the testing of this reflex.
  • Response is brisk closure of both the eyes
  • Stimulation should elicit both a direct and indirect or consensual response (opposite eye). The reflex consumes a rapid rate of 0.1 second. The evolutionary purpose of this reflex is to protect the eyes from foreign bodies

An absent corneal reflex may be due to
  • Sensory loss in Vi (e.g. neuropathy or ganglionpathy)
  • Weakness or paralysis of the facial muscles (myopathy) 
  • Facial nerve (facial palsy, for example Bell's palsy) 
  • Brain stem disease.
For a myopathy to cause a loss of the blink reflex the weakness has to be very severe, example  chronic progressive external ophthalmoplegia (CPEO)

How to elicit Conjunctival reflex?

Method of elicitation
  • Stand on one side of the subject and ask him to look at a far object on the opposite side.
  • A sterile piece of cotton is twisted into a wisp and bring it from the back of the subject avoiding his visual attention.
  • Touch the conjunctiva and see the response. Both eyes are separately tested.
  • Observation: Bilateral closure of the eyes. Reflex pathway
  • Receptors: Touch receptors of the conjunctiva
  • Afferent limb: Ophthalmic division of trigeminal nerve
  • Efferent limb: Facial nerve
  • Effector muscle: Orbicularis oculi
  • Centre - Pons (Nucleus of Trigeminal Nerve)

Interpretation of tendon reflexes

Tendon reflexes are graded as follows
Grading of reflexes
  • grade 0; absent
  • grade 1: sluggish
  • grade 2: normal normal like ankle jerk
  • grade 3: brisk - normal kneejerk
  • grade 4: exaggerated
  • grade 5: clonus
Causes of absent deep tendon reflex
Causes of Hyporeflexia
Causes o f Brisk or exaggerated reflex
Pendular reflex
Hung-up reflex
Delayed relaxation of reflex
Inversion of reflex 

Causes of absent tendon reflexes:

Tendon reflex may be absent in the following situations
  • Lower motor neurone disease
  • Neuronal shock
  • Marked spasticity and muscle contracture
  • Normal individuals unable to relax
It is  seen in lower motor neuron lesions involving  any part of the reflex arc
  • Lesion of the sensory nerve (polyneuritis)
  • Lesion of the sensory root (tabes dorsalis)
  • Lesion of the anterior horn cell (poliomyelitis)
  • Lesion of the anterior root (compression)
  • Lesion of the peripheral motor nerve (trauma, polyneuritis).
Before labelling as absent reflex do reinforcement

What are the common causes of Hyporeflexia?

Hyporeflexia is a condition characterized by the absence or diminished reflex in reaction to an applied stimulus. This condition is associated with the lower motor neuron disease defined by a deficit in the nerve that runs through the spinal cord going to the extremities.
Hyporeflexia is the hallmark of LMN lesion .It is also seen in UMN shock
LMN lesions
  • AHC
  • Root
  • plexus
  • nerve
  • muscle
  • Neurological shock
  • Severe extrapyramidal rigidity
  • Contracture
  • Peripheral neuropathy
  • GBS
  • SACD
  • Tabes dorsalis
  • Friedreich's ataxia
  • Periodic paralysis
  • Cerebral or spinal shock

Isolated loss of a rellex usually suggests radiculopathy.
Symmetrical loss of rellex may be found in peripheral neuropathy.
Reflexes may be absent if the patient is unable to relax.
A reflex seems lost or diminished in defect of technique, relaxation, or observation.

Inverted Reflexes clinical significance

Invertion of Radial Reflex
  • On eliciting the supinator jerk, the following response is observed
  • There is absence of flexion of  elbow, 
  • Instead there is brisk finger flexion,
  • Biceps jerk is absent and the triceps jerk is exaggerated. The presence of this lesion suggest this the
  • Lesion at  C5>C6 segment.
Invertion of Biceps Reflex
  • On eliciting bicep reflex the following are noticed 
  • There is no flexion at the elbow
  • But instead there is extension at the elbow' due contraction of the triceps muscle.
  • Presence of this  reflex indicates that the lesion is at the level of C5 segment
Invertion of Knee Reflex
  • On eliciting the knee jerk you can observe the following
  • There is no extension of the knee joint 
  • But instead there is flexion of the knee due to contraction of the hamstring muscles. 
  • Presence of this indicates that the lesion is at the level of L3, 4

How to do reinforcement of tendon reflex

Reinforcement Upper Limb is done with 
  • Clenching teeth
  • Clenching fist on the other side
Reinforcement of lower Limb is done with 

What is Pseudomyotonic Reflex

It is a delayed muscle relaxation after brisk contraction the muscle on elicitation of the deep tendon reflex,best seen on eliciting the ankle jerk.
  • It is classically seen in myxedema 
  • It is also seen with administration of Beta blockers  and in hypothermia.

Technique of elicitation of deeptendon reflex

In a screening examination you it more convenient to integrate the reflex examination into the rest of the examination of that part of the body; that is, do the lower extremity reflexes when examining the rest of the lower extremity. When there is an abnormality of the reflexes is noted , however, the reflexes should be examined as a group with careful attention given to the technique of the examination.
Reliable test results are best obtained when the patient is fully relaxed
Explain the procedure to the patient
  • If you fails to get any response with a specific reflex that can usually occcur with ankle jerks then try the following:
  • Several different positions of the limb.
  • Get the patient to put slight tension on the muscle being tested. One method of achieving this is to have the patient strongly contract a muscle not being tested.
  • In the upper extremity, have the patient make a fist with one hand while the opposite extremity is being tested.
  • If the reflex being tested is the knee jerk or ankle jerk, have the patient perform the "Jendrassik maneuver," a reinforcement of the reflex . The patient's fingers of each hand are hooked together so each arm can forcefully pull against the other. The split second before you are ready to tap the tendon, say "pull."
  • In general, any way to distract the patient from what you are doing will enhance the chances of obtaining the reflex. you can instruct the patient to count or give the names of children are examples.
The best position to elicit reflex is that the patient to be sitting on the side of the bed or examining table. The Babinski reflex hammer may be used..
  • Use a brisk but not painful tap. 
  • Use your wrist, not your arm, for the action. 
  • In an extremity a useful maneuver is to elicit the reflex from several different positions, rapidly shifting the limb and performing the test. Use varying force and note any variance in response.
  • After obtaining the reflex on one side, always go immediately to the opposite side for the same reflex so that you can compare them.
You should note the following features of the reflex response:
  • Amount of hammer force necessary to obtain contraction
  • Velocity of contraction
  • Strength of contraction
  • Duration of contraction
  • Duration of relaxation phase
  • Response of other muscles that were not tested. When a reflex is hyperactive, that muscle often will respond to theexamination of a nearby muscle. A good example is reflex activity of a hyperactive biceps or finger reflex when the brachioradialis tendon is tapped. It is termed "overflowing" of a reflex.

Causes of Exaggerated tendon reflex

In hyperactive stretch reflex there is increased speed of response, duration and amplitude of movement.
  • Hyperreflexia can be either exaggerated or brisk response.it is very difficult to differentiate between the two. The term exaggerrated reflex means tbe amplitude and duration of the limb movement is more and brisk rellex means an increase in amplitude but not increase in duration,Brisk reflex may be a normal variant its presence may confuse us as abnormal but  is only of pathological significance when it is asymmetrical (comparing with the other side) or if associated with other signs of UMN lesion (spasticity. Babinski’s sign etc.)
Brisk       = Increase in amplitude of muscle contraction
Exaggerated = Increase in amplitude and duration of musle contration
  • Hyperactivity of muscle indicate an interruption of corticospinal and other descending pathways that influence the reflex arc due to a suprasegmental lesion, that is, a lesion above the level of the spinal reflex pathways.
Hyperactivity of muscle reflex is seen in the following conditions
  • As a sign of UMN lesion - pyramidal lesion and associated damage of reticulospinal and vestibulo spinal tract.
  • Psychoneurosis - anxiety -amplitude of movement is increased.Reflexes may be brisk if the patient is agitated, frightened, or anxious.
  • Tetany
  • Tetanus
  • Early phase of neuritis - increased irritability of peripheral nerve
  • Paralysis of antagonist - increased knee jerk in paralysis of antagonist hamstring muscle
  • Extrapyramidal lesion - increased tension of muscle (not always). MSR slightly increased
  • Thyrotoxicosis.
  • Strychnine poisoning 
When the reflexes are exaggerated, always look for clonus

What is the relationship between Clonus and spasticity

Spasticity often occurs with clonus. It involves long-term muscular tightness.

Spasticity, as seen in clonus, is produced  by damaged nerves among the brain, spinal cord, and muscles. This abnormal activity is disrupt muscle movement by causing involuntary contractions, stiffness, and pain.

Neurological and muscular issues that can occur alongside clonus can include:
  • Overactive deep tendon reflexes
  • Fixed joints, known as contractures
  • Hypertonicity
  • Scissoring-Involuntary leg-crossing, sometimes called scissoring

Wrist Clonus

Clonus, is usually encountered in the knee or ankle, it is a classic symptom of spasticity occurring as a result of lesions in upper motor neurons.
Wrist clonus significance is that it is much less common and can be confusing and misdiagnosed. Wrist clonus in patients affected with hemiplegia was described in lectures published in 1883 by the French neurologist Jean-Martin Charcot, who called this  phenomenon  as “provoked trepidation” and noticed that .These patients, on raising the paralysed arm, often experience a trembling similar to that which occurs in the lower limb under like circumstances. But the wrist-phenomenon, provoked or spontaneous, is much more uncommon.”
Method of elicitation of wrist clonus
Hyperextend the wrist, sustained pressure is applied.
There is sustained clonic movement of the hand induced by sudden extension of the wrist.

Ankle clonus -A complete guide

Clonus is a series of involuntary, rhythmic, muscular contractions and relaxations. Clonus is a sign of upper motor neuron lesions involving descending motor pathways,
Ankle clonus is an involuntary tendon reflex that causes repeated flexion and extension of the foot. . More than four beats of clonus is pathological.It is the grade 4 ankle hyper reflexia.
There is repetitive ankle dorsiflexion and plantarflexion on passive dorsiflexion of the foot by the examiner till the force applied by the examiner is withdrawn.
Method of elicitation of  ankle clonus
  • Patient lies supine. 
  • Support the flexed knee with your left palm (placed in the popliteal fossa) (with both the knee and ankle resting in 90° flexion)
  • Now briskly dorsiflex and partially evert the foot with your right hand sustaining the pressure (do not leave the hand after dorsiflexing). (heel should not touch the bed). 
  • A series of contraction and relaxation of calf muscles are seen if a steady pressure is maintained on the foot by the right hand. Clonus is felt as repeated beats of dorsiflexion/plantar flexion.

Pathogenesis of ankle clonus
Ankle clonus is seen in people with damage to the neuronal pathways in the spinal cord or brain (an upper motor neurone lesion), elicited by a deliberate rapid, stretching of the ACHILLES TENDON, by forcibly flexing the foot. There is a rhythmic contraction of the calf muscles following a sudden passive dorsiflexion of the foot, the leg being semiflexed.The spinal reflex arc is intact but the normal control on it, from above, is abnormal.
Causes of ankle clonus
Any spinal cord lesions, be it traumatic, neoplastic, pyogenic, vascular above the level of S1 can cause clonus.
This is because of the spasticity caused by the UMN type of injury causing hyper reflexia and clonus. Some other causes of clonus are
  • Meningitis
  • Tetanus
  • CJD
  • Cerebral palsy
  • Multiple sclerosis
  • Syringomyelia
  • Pre-eclampsia
  • Ankle clonus:

How to elicit plantar reflex?

Plantar response is a local reflex arc modified by the pyramidal tract.
Position of the patient
All the leg muscles should be visible and in a relaxed state. It can be achieved by positioning the patient in a way that the knee is slightly flexed and the thigh is externally rotated. The patient should be warned that the sole is going to be scratched and ask him to try to let his limb remain as floppy as possible. You should not be touched the toes.
Many factors can influence the clinical response including the site of stimulation, the intensity of stimulation, and even the object used for stimulation . Any part of the leg can be stimulated, but the best technique is to stimulate the lateral plantar surface and the transverse arch in a single movement upto the middle metatarsophalangeal joint with a firm applicator lasting 5 to 6 seconds.
Method of elicitation of elicitation of plantar reflex.
  • The patient lies supine with extended legs and there should be relaxation of the muscles of the Iower limb.
  • Hold the leg firmly above the ankle joint with examiners  left hand 
  • The outer border of the sole is scratched gently by a key (preferable). stick of the hammer or blunt needle. 
  • Starting from the heel, go along the lateral border towards the little toe and then turn medially across the metatarsus upto the head ol 2nd metatarsus in a semicircular fashion. 
  • You should never touch the ball of the great toe and the flexor creases of the toes.
  • The stimulus should not produce injury but it should be of noxious character as  this is a ‘nociceptive reflex'. 
  • You should stop stimulating the sole as soon as you get the first movement of the great toe.
  • Now do the test on the other side. 
What are the precautions taken before eliciting plantar response ?
  • You should assess the following before checking the reflex
  • Assess the thickness of the sole—Thick sole may be responsible for absent response .
  • Look for any deformity of great toe—Move the great toe. and confirm that it is moving freely and
  • It is not rigid.
  • Knee must be extended.
  • Sole should be made warm (eg. by rubbing with your palm, specially in winter seasons
  • Leg should lie straight  don't allow rotation of thigh.
  • One may assess the power of extensor hullucis longus before doing the test (optional).

What is the root value of this reflex ?
Why the lateral aspect of the sole is stimulated ?
1.Lateral aspect of the sole is preferred because the receptors for extensor plantar response are present there in abundance and hence,even. In minimal UMN lesion, extensor plantar response is obtained  by stimulating the lateral aspect of the sole.
2. If the  medial aspect of the sole is stimulated, it may elicit flexion (even in the presence of UMN
lesion) of all the toes as part of the grasp relex,which is a different phenomenon.

Cause of extensor plantar response with loss of ankle jerk

Extensor plantar response is usually associated with brisk ankle reflex .But in certain conditions the plantar response is extensor with absent ankle jerk
  • Subacute combined degeneration.
  • Taboparesis (CPI plus tabes dorsalis).
  • Friedreich's ataxia.
  • Cauda-equina lesion (cauda equina lesion with lesion in conns medullaris)
  • Combined cervical and lumbar spondylosis
Plantar response is flexor with brisk ankle jerk
Sometimes it is observed in anxiety  and thyrotoxicosis (exaggerated deep reflex).

Tromner Reflex – Clinical significance

What is the method of elicitation of Tromner sign
  •  Fix the proximal middle phalanx
  • Tap volar surface of the finger

Positive Tromner sign indicate the tip of the fingers flex and the thumb flexes and adducts
This is an early sign of pyramidal disease

Tricep jerk- a complete guide

Tricep jerk is an example of deep tendon reflex.
Method of elicitation of tricep jerk?
Place the patients hand over his chest with the elbow flexed.
Support the hand at the wrist by your left hand so that the upper limb does not fall on the bed. Suddenly tap above the olecranon process ie on the tricenp tendon 5 cm above the elbow (never tap on the muscle)
Observe the following response
  • Contraction of triceps 
  • Slight extension of the elbow.

Innervation  of Triceps Jerk 
Innervation of tricep jerk C7-C8
Nerve  -Radial nerve
What is Paradoxic triceps reflex: 
This consists of flexion instead of extension of the forearm following stimulation of the triceps tendon.
This response  appears when the arc of the triceps reflex is damaged
Occur  in lesions of seventh and eighth  cervical segments in such cases the stimulus calls forth a flexor response unopposed by the triceps muscle.
Paradoxical Triceps jerk is characterised by the following
  • Absent triceps
  • A flexion of forearm
  • It indicate a lesion at C7

Clonus and its clinical signifiance

Rhythmic reflex monophasic contractions and relaxations of hypertonic muscles in response to an abruptly applied and sustained strecth stimulus
Clonus is a rhythmical series of contractions in response to the maintenance of tension in a muscle, associated with increased gamma efferent discharge. It is elicitable when tendon reflexes are brisk after a corticospinal lesion
The word Clonus  comes from the Greek word  meaning "violent, confused motion. Significance  of clonus is that it is a sign of neurological conditions, epecially associated with upper motor neuron lesions involving descending motor pathways
Clonus is a condition that produce involuntary muscle spasms and most commonly it affects the muscles at the end of a limb. Clonus mainly affects the knees, ankles, upper and lower arm muscles, and the jaw.
The basic abnormality in clonus is
1. alternate involuntary muscular contraction and relaxation in rapid succession.
2. a continuous rhythmic reflex tremor that is initiated by the spinal cord below an area of spinal cord injury, when set in motion by reflex testing.
Mechanism of clonus
The exact mechanism of clonus remains unclear. Two different hypotheses have been asserted regarding the development of clonus.
  • The most widely accepted explanation is that hyperactive stretch reflexes in clonus are caused by self-excitation. 
  • Another alternative explanation for clonus is central generator activity that arises as a consequence of appropriate peripheral events and produces rhythmic stimulation of the lower motor neurons.

What are the association of clonus?
Clonus is always associated with
  • Brisk tendon reflex. 
  • Spasticity and
  • Bablnski's sign-It is a very reliable sign of pyramidal tract lesion. 
There arc two types of clonus :
  • Sustained clonus (true clonus).
  • Unsustained clonus (pseudoclonus).
Unsustained clonus (≤5 beats): may be physiological
Sustained clonus (>5 beats): regarded as abnormal

Sites for clonus examination  in clinical neurology :
  • Ankle clonus.
  • Patellar clonus.
  • Jaw clonus (elicit the Jaw jerk to see a scries of closure and opening of the mouth).
  • Wrist clonus (elicited by sudden passive extension of the fingers).
3 and 4 are not routinely practised in clinical neurology.

Medical conditions that can cause clonus include:
  • Multiple sclerosis
  • Huntington disease
  • Spinal cord or brain injuries
  • Stroke
  • Meningitis
  • Cerebral palsy
Difference between a organic and non organic clonus

Organic clonus          Functional clonus
Sustained                         Non sustained
Bilateral equal                 Unequal
Exaggerated reflexes       Absent
Plantar extensor          Flexor