BLINK REFLEX BY CK

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Blink reflex study, and blink reflex abnormal cases

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BLINK REFLEX:

BLINK REFLEX By: Chaman Lal Karotia (CK) CNPT (AKUH), R.EEGT, BS.PT,MPPS(PAK) Member of AANEM & ASET (USA) CLINICAL NEUROPHYSIOLOGY DEPARTMENT AKUH, KARACHI.

-:Study Outlines:-:

-:Study Outlines:- Definition of Reflex Activity Introduction to Blink Reflex Anatomical Description of the Relating Structures Indication for Blink Reflex Study Standard Recording Parameters Procedure Recording Techniques Normative Values & Interlatencies Comparisons Abnormal Patterns References 2 Blink Reflex By: AJ & CK

Reflex:-:

Reflex:- Definition:- An EFFERENT response to an AFFERENT stimulation is known as reflex. Its also known as reflex arc response because there is an afferent segment, synapses with interneurons and then there is an efferent limb, all these making an arc of activity hence called Reflex Arc Response. 3 Blink Reflex By: CK

INTRODUCTION:- :

INTRODUCTION:- Blink reflex is an electrical equivalent of corneal reflex. Blink reflex is capable of evaluating the cranial nerves and their proximal segments. Cranial nerves V (trigeminal) and VII (facial), along with their connections in the Pons and medulla, can be assessed electrically with the blink reflex. Like H reflex, the blink reflex is a true reflex, with a sensory afferent limb, interneuron synapses, and a motor efferent. 4 Blink Reflex By: CK

CONT…:

CONT… The blink reflex is an excellent electrophysiological technique for the evaluation of demyelinating Neuropathies, compression of peripheral facial and trigeminal nerves may be detected as well as central lesion in the brain stem 5 Blink Reflex By: CK

ANATOMICAL DESCRIPTION:-:

ANATOMICAL DESCRIPTION:- The afferent limb of the blink reflex is mediated by sensory fibers of the supraorbital branch of the ophthalmic division of the trigiminal nerve ( cranial nerve V ) and the efferent limb by motor fibers of the facial nerve ( cranial 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. 6 Blink Reflex By: CK

CONT…:

CONT… Stimulation of the ipsilateral supraorbital nerve results in an afferent volley 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. 7 Blink Reflex By: CK

CONT…:

CONT… The blink reflex has two components, an early R1 and late R2 responses. The R1 response is usually present ipsilateral to the side being stimulated, whereas the R2 responses are typically present bilaterally. 8 Blink Reflex By: CK

CONT…:

CONT… The R1 response is thought to represent the disynaptic reflex pathway between the main sensory nucleus of V in the mid Pons and the ipsilateral facial ( VII ) nucleus in the lower pontine. The R2 responses are mediated by a multisynaptic pathway between the nucleus of the spinal tract of V in the ipsilateral Pons and medulla,& interneuron’s forming connection to the ipsilateral & contralateral facial ( VII ) nuclei. 9 Blink Reflex By: CK

CONT…:

CONT… The earlier R1 response is usually stable and reproducible, with a bi- or triphasic morphology. The R2 responses, on the other hand, are polyphasic and variable from stimulation to stimulation. 10 Blink Reflex By: CK

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CONT….:

CONT…. The afferent loop of the blink reflex is mediated by the first division of the trigiminal nerve (V) which synapse with both the main sensory nucleus of cranial nerve V ( V M ) in the mid Pons and with the nucleus of the spinal tract of the cranial nerve V ( Vs ), in the medulla. 12 Blink Reflex By: CK

CONT…:

CONT… The earlier R1 potential is mediated by the disynaptic connection between the main sensory nucleus and the ipsilateral facial motor nucleus ( VII ). The late R2 responses are mediated by a multisynaptic pathway between the nucleus of the spinal tract of cranial nerve V and both ipsilateral and contralateral facial nuclei ( VII ). 13 Blink Reflex By: CK

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Indication for Blink Reflex:-:

Indication for Blink Reflex:- Lesions of the V nerve Facial /Bells palsy Synkinesis of facial muscles Hemi facial spasm Acoustic neuroma Polyneuropathy Lesions in brain stem and spinal cord Multiple Sclerosis Wallenberg syndrome 15 Blink Reflex By: CK

STANDARD RECORDING PARAMETERS:-:

STANDARD RECORDING PARAMETERS:- Sweep speed is set at 5 or 10 msec/division Sensitivity is set at 100 or 200 µV/division Electrical pulse of 100 µs duration is used Motor filter settings are 10Hz & 10KHz 16 Blink Reflex By: CK

PROCEDURE TECHNIQUE:-:

PROCEDURE TECHNIQUE:- Recording is performed from both side simultaneously using a two channel recording apparatus. G1-Surface recording electrodes or active electrodes are placed over the inferior orbicularis occuli muscles bilaterally. 17 Blink Reflex By: CK

CONT…:

CONT… G2 - The corresponding reference electrode are placed just lateral to lateral canthus bilaterally, OR A reference electrode is placed on nose/chin. The ground electrode is placed on the forehead. 18 Blink Reflex By: CK

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NORMATIVE:-Electrodiagnosis In Diseases of Nerve By: JUN KIMURA 3rd Ed:

Response Latency Ranges Ipsilateral R1 10.5-13.0 ms Ipsilateral R2 30.5±40.0 ms Contralateral R2 30.5±41.0 ms L/R  R1 ≤ 1.2 ms Ipsilateral R1  R2(contra) ≤ 5.0 ms Contralateral R2  R2 ≤ 7.0 ms NORMATIVE:- Electrodiagnosis In Diseases of Nerve By: JUN KIMURA 3 rd Ed 21 Blink Reflex By: CK

NORMATIVE:- (Preston 2nd Ed.):

Response Latency Ranges Ipsilateral R1 ≤13.0 ms Ipsilateral R2 ≤41.0 ms Contralateral R2 ≤44.0 ms L/R  R1 ≤ 1.2 ms Ipsilateral R1  R2(contra) ≤ 5.0 ms Contralateral R2  R2 ≤ 7.0 ms NORMATIVE:- (Preston 2 nd Ed.) 22 Blink Reflex By: CK

Normative in Neonates:-:

Normative in Neonates:- In normal neonates, the latencies and amplitudes were 10.9 ± 0.7 msec and 159 ± 62 μV at R 1 , 34.3 ± 1.4 msec and 123 ± 30 μV at R 2 , and 40.7 ± 2.3 msec and 84 ± 25 μV at R' 2 respectively. Ischemic-hypoxic brain damage during the neonatal period mainly influenced the late components of the blink reflex. The blink reflex of the postasphyxial neonates showed significantly prolonged latencies of R 2 & R' 2 . The amplitudes were increased in cases with a fair prognosis & decreased in cases with a poor prognosis. The blink reflex in neonates appears to be useful in predicting the outcome in cases of neonatal asphyxia & congenital hydrocephalus. ( J Child Neurol 1987;2:287-292). Study: “Prognostic Significance of the Electrically Elicited Blink Reflex in Neonates” *Tomoko Tanaka, MD, Yutaka Tomita, Satoko Nishimura Division of Child Neurology, Institute of Neurological Sciences, Tottori University School of Medicine, Yonago , Japan 23 Blink Reflex By: CK

Normative Comparison:-:

Normative Comparison:- Side to side R1 latency difference should not exceed 1.2 ms R2 (ipsi) and R2 (cont) latency difference when stimulated from one side should not vary > 5ms. 24 Blink Reflex By: CK

Normative Comparison……cont’d:

Difference between R2 (ipsi) when stimulated from one side and R2(cont) from stimulated from other side should not be >7ms. R/D latency ratio = 2.6 – 4.6  2 SD. 25 Normative Comparison……cont’d Blink Reflex By: CK

  ABNORMAL PATTERNS:- :

ABNORMAL PATTERNS:- Many different patterns of abnormalities can occur depending on the site or sites of the lesion (s). The basic abnormal patterns are as follow: 26 Blink Reflex By: CK

1.UNILATERAL TRIGEMINAL LESION:-:

1.UNILATERAL TRIGEMINAL LESION:- Unilateral trigeminal lesion stimulating the affected side, there will be a delay or absence of all potentials (ipsilateral R1 and R2,contralateral R2). Stimulating the unaffected side results in normal potentials, including the ipsilateral R1 and R2 and the contralateral R2. 27 Blink Reflex By: CK

2.UNILATERAL FACIAL LESION:-:

2.UNILATERAL FACIAL LESION:- 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. 28 Blink Reflex By: CK

3.UNILATERAL MIDPONTINE LESION:-   :

3.UNILATERAL MIDPONTINE LESION:- 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 R1, but an intact ipsilateral and contralateral R2. Stimulating the unaffected side results in all normal potentials, including R1 and ipsilateral and contralateral R2. 29 Blink Reflex By: CK

4.UNILATERAL MEDULLARY LESION:- :

4.UNILATERAL MEDULLARY LESION:- 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. 30 Blink Reflex By: CK

CONT…:

CONT… If there is a more extensive lesion in the medulla involving medullary interneuron’s to the contralateral facial nerve: Stimulating the affected side will result in a normal R1,but both the ipsilateral and contralateral R2 potentials will be absent or delayed. Stimulating the unaffected side results in the same pattern. 31 Blink Reflex By: CK

5. DEMYELINATING PERIPHERAL NEUROPATHY:- :

5. DEMYELINATING PERIPHERAL NEUROPATHY:- Blink reflex can be affected in Demyelinating peripheral neuropathy. Axonal neuropathies rarely affect the blink reflex because typical axonal distal dying-back neuropathies are unlikely to affect the fibers that mediate the blink reflex, which are so proximal. 32 Blink Reflex By: CK

Cont’d…:

Cont’d… However, in demyelinating neuropathies, all potentials of the blink response may be markedly delayed or absent, reflecting slowing of either or both motor and sensory pathways. 33 Blink Reflex By: CK

Cont’d…:

With an understanding of the anatomy of the blink reflex circuitry and the basic abnormal patterns outlined here, one can extrapolate the patterns of abnormalities for more complex lesions (e.g., bilateral pontine, bilateral medullary). 34 Blink Reflex By: CK Cont’d…

References::

References: Electromyography & Neuromuscular Disorders By David C. Preston 2 nd Edition. Kimura J. Electodiagnosis in diseases of Nerve& Muscles Philpidia F.A Davis 1989. Shahani BT, Young RR. Human Orbicularis Oculi reflexes Neurology. Snell’s Human anatomy “Cranial Nerves Anatomy & Pathways” 24 th Ed. 35 Blink Reflex By: CK

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