blink reflex in NCV

1. IM 18-07-
2012.

3. IM 18-07-
2012.
• Definition:-
Reflex is an efferent response to an afferent
stimulation.
• Its also known as reflex arc response because
there is an afferent segment, synapses with
inter-neurons and then there is an efferent
limb, all these making an arc of activity hence
called Reflex Arc Response.

4. IM 18-07-
2012.
INTRODUCTION :
Blink reflex
correlate of
reflex.
is essentially
the clinically
the
evoked
electrical
corneal
Blink reflex is capable of evaluating the cranial
nerves and their proximal segments.
The afferent limb of blink reflex is ophthalmic
division of trigeminal (V) nerve (which can be
stimulated mechanically or electrically) and
the facial (VII) nerve mediates the efferent
arc.

5. IM 18-07-
2012.
Advantages
• The blink reflex study
electrophysiological technique
is a useful
for the
evaluation of patients with:
• ● Involvement of trigeminal or facial nerve.
• ● Variety of demyelinating polyneuropathies
• ● Central Lesion in the Brainstem

6. IM 18-07-
2012.
Anatomy
• The afferent limb of the blink reflex is
mediated by sensory fibers of the supraorbital
branch of the ophthalmic division of the
trigiminal nerve (V) and the efferent limb by
motor fibers of the facial nerve (VII).
• Just as with the corneal reflex, ipsilateral
electrical stimulation of the supraorbital
branch of the trigiminal nerve elicits a facial
nerve (eye blink) response bilaterally.

7. IM 18-07-
2012.
Application Methods
Position of Patient:
Lying on the couch with eyes closed.
Recording Electrodes :
Active electrode placed laterally over the
orbicularis occuli muscles
Reference placed on the side of the nose, OR
Chin.
Ground Electrode : Placed submentally on the
neck or forehead.

8. IM 18-07-
2012.
Stimulating Site
Supraorbital nerve is stimulated which is the
branch of Trigeminal Nerve (Cranial Nerve V)
with cathode placed over the supra-orbital
foramen/notch on one side and anode placed
on the forehead.

9. IM 18-07-
2012.
PARAMETERS
SWEEP TIMEVE/LOCITY: 5-10 (msec/div)
• SENSITIVITY: 200 (µv/div)
• FILTERS: (HFF:20Hz, LFF: 10KHz)
• STIMULATION DURATION/RATE: 0.01msec/2 Hz
• INTERVAL : Between successive stimuli is set at
atleast 30 sec to minimize interactions between
them.
• (If R1 is not recorded easily, reduce the
interstimulus interval to 5msec so that facilitation
resulting from first stimulus permits R1 to be
elicited.)

10. BY IM/EK. 18-07-2012
10

11. 2012.
Response to Electrical Stimulus
• Stimulation of the ipsilateral supraorbital
nerve results in an afferent response along the
trigiminal nerve to both the main sensory
nucleus of V (mid Pons) and the nucleus of the
spinal tract of V (lower Pons and medulla) in
the brain stem.
• Through a series of interneuron’s in the Pons
and lateral medulla, the nerve impulse next
reaches the ipsilateral and contralateral facial
nuclei, from which the efferent signal travels
along the facial nerve bilaterally.
IM 18-07-

12. IM 1812-07-
2012.

13. IM 18-07-
2012.
REFLEX RESPONSE
• Two distinct components are there, which as following
1. EARLY R1
2. LATER R2
• 1. EARLY R1 COMPONENT:
• Elicited only on the side that is stimulated. Relatively
stable. Short lasting and of low amplitude. A disynaptic
pathway between the main sensory nucleus of the
trigeminal nerve and the ipsilateral facial nucleus.

14. IM 18-07-
2012.
Cont,
2. LATER R2 COMPONENT
Present on both sides following unilateral
stimulation.
More variable.
Long lasting and of higher amplitude.
A polysynaptic connections between the spinal
nucleus of the trigeminal nerve and bilateral
facial nucleus.

15. IM 18-07-
2012.
REFLEX RESPONSE
• EARLY R1 COMPONENT:
• If latency > 13ms, then its abnormal
• Interside difference in latency < 1.2ms.
• LATER R2 COMPONENT:
• If ipsilateral latency > 41ms and contralateral
latency > 44ms, then its abnormal.
• The latency difference between ipsilateral and
contralateral response recorded simultaneously
following unilateral stimulation is < 5ms.
• The latency difference between R2 evoked by
stimulation on each side in turn should be < 7ms.

16. IM 18-07-
2012.
REFLEX RESPONSE
• EARLY R1 COMPONENT:
• Delay or absence indicates a disturbance of
trigeminal or facial nerve or both on that side.
• LATER R2 COMPONENT:
• Involvement of R2 indicates the site of lesion
when R1 is abnormal.
• Trigeminal nerve lesions is characterized by
bilateral delay or attenuation of R2 when the
affected side of the face is stimulated.
• Facial nerve lesions is characterized by delay of R2
on the affected side, whichever side is stimulated.

17. IM 18-07-
2012.
BLINK REFLEX INDICATION
• Facial /Bells palsy (facial paralysis resulting from a dysfunction of the cranial nerve
VII (the facial nerve)
• Polyneuropathy
• Lesions of the V nerve
• Synkinesis of facial muscles (involuntary movements due to miswiring of
nerves after trauma)
• Hemi facial spasm (frequent involuntary contractions)
• Acoustic neuroma (slow-growing tumor of the nerve that connects the ear to
the brain (cochlear nerve))
• Lesions in brain stem and spinal cord
• Multiple Sclerosis (a chronic autoimmune disorder affecting movement,
sensation, and bodily functions, caused by destruction of the myelin insulation covering
nerve fibers (neurons) in the CNS )
• Wallenberg syndrome (difficulty in swallowing and hoarseness due
to paralysis of the ipsilateral vocal cord.)

18. IM 18-07-
2012.
CLINICAL APPLICATION
In Bell’s Palsy, the response is initially nearly
normal becoming abnormal after few days. R1 -
delayed or abnormal during the first few weeks
suggesting demyelination.
In certain polyneuropathies - Direct response
and R1 component delayed.
In comatose patients and acute phase of CVA -
R2 delayed.

19. IM 18-07-
2012.
CLINICAL APPLICATION
• In hemifacial spasm or facial synkinesis following
aberrant reinnervation there is spread of blink
reflex into muscles other than orbicularis oris.
• In multiple sclerosis, the R1- delayed on one or
both the sides and alterations in the R2
component is less specific. And if R2 is abnormal
(with normal R1), it is suggestive of lateral
medullary lesion.
• In Wallenberg’s syndrome, the R1 - normal and
R2 - delayed or absent bilaterally with the
stimulation of the affected side of the face

20. BLINK REFLEX PATTERNS
NORMAL BLINK RESPONSE: Intact trigiminal and facial nerve
IM 18-07-
2012.

21. (ipsilateral R1 and R2,contralateral R2).
Stimulating the unaffected side results in normal
Unilateral trigeminal lesion: Stimulating the affected
side, there will be a delay or absence of all potentials
potentials, including the ipsilateral R1 and R2 and the
contralateral R2.
IM 18-07-
2012.

22. Unilateral facial lesion: Stimulating the affected side
results in delay or absence of the ipsilateral R1 and
R2,but a normal contralateral R2.
Stimulating the unaffected side results in a normal
ipsilateral R1 and R2,but delayed or absent
contralateral R2.

23. Unilateral midpontine lesion (main sensory nucleus V and/or
lesion of the pontine interneuron’s to the ipsilateral facial
nerve nucleus) or both.
Stimulating the affected side results in an absent or delayed
Stimulating
R1, but an intact ipsilateral and contralateral R2.
the unaffected side results in all normal
potentials, including R1 and ipsilateral and contralateral R2.

24. • Unilateral medullary lesion (interneuron’s to the
ipsilateral facial nerve nucleus).
• Stimulating the affected side results in a normal
R1 and contralateral R2, but an absent or delayed
ipsilateral R2.
• Stimulating the unaffected side results in normal
ipsilateral R1 and R2 potential, but a delayed or
absent contralateral R2.
IM 18-07-2012.

25. Blink reflex can be affected in Demyelinating
peripheral neuropathy.
In demyelinating neuropathies, all potentials
of the blink response may be markedly delayed
or absent, reflecting slowing of either or both
motor and sensory pathway
IM 18-07-

26. Bilateral Trigeminal Nerve Nucleus
lesion: Stimulating on either side will
result in delayed/absent Ipsi R1
bilaterally. While bilateral Ipsi R2 and
Contra R2 will remain preserved.
IM/EK 18-07-
2012.

27. Diligence is the mother of good fortune.
IM/EK 18-07-
2012.
• EMG AND NEUROMUSCULAR DISORDER BY
David C. Preston
• Snell’s Human anatomy
• Kimura J. Electodiagnosis in diseases of
Nerve& Muscles
REFERENCES