Date post: | 07-May-2015 |
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Neuro-Clinics 31The pupils
Dr Pratyush Chaudhuri
Supported by Nirmal Clinics
Basics
• Pupils are controlled by constrictor fibres supplied by parasympathetic nerves.
• Radial fibres controlled by sympathetic fibres
Basics
• Resting size depends on the amount of light falling on the eye and depends on the integrity of the parasymapthetic system.
• Increased activity of the symapathetic system is reflected in the slight dilatation of the pupils.
• Small pupils are asymptomatic because of ability to focus close.
• Dilated pupils cause blurring of vision o close vision.
Parasympathetic pathway
Afferent pathway lesion
Marcus Gunn Pupil
• When the eye is stimulated with bright light – there will be sustained constriction of pupil
• If the abnormal eye is stimulated there will be an ill-sustained constriction followed by dilatation. (Pupillary escape phenomenon)
Due to decrease in the number of fibers sub serving the light reflex.
Wernike’s pupillary reaction
• A lesion of one side optic tract affects the direct reflex
• but if properly shown properly to the unaffected half of the same eye – reflex may be elicited.
• Lesions compressing or infiltrating the tectum of the midbrain (area of the sup collicular bodies) will interfere with the decussating fibers o the peri-aqueductal area
• Results in fixed semi-dialted pupils with loss of upward gaze.
Parinaud syndrome
Argyll Robertson pupil
• Small irregular , fixed to light but reactive to accomodation
• Due to lesion in the Edinger Westphal Nu
• Causes – neurosyphilis, pinealomas, diabetes, wernicke’s encephalopathy, brainstem encephalitis and multiple sclerosis.
• Cannot be dilated with atropine
Reverse Argyll Robertson pupil
• Rare
• Asociated with epidemic encephalitis lathergica
• Pupils react to light but not to accomodation.
Adie pupil or tonic pupil
• Possible viral cause• Associated with loss of sweating and knee
jerks
• Widely dilated circular pupil that may react very slowly to very bright light but more definite to accomodation.
Sympathetic pathways
• Starts in the hypothalamus• Considerable degree of cortical ipsilateral control
Three neurons1. Hypothal to lateral grey in sp cord C8 -T1 – celio-spinal centre of
Budge2. From spinal cord to superior cervical ganglion via white rami of
nerve root C8 – T13. From superior cervical ganglion to the blood vessels and pupil
activity
• Innervate sup and inferior tarsus muscles of Muller and orbitalis (causes “upside down’’ ptosis)
• Nasociliary vasomotor fibers --- ciliary ganglion---- blood vessels of the eye.
• Pupillo-dilatation
Abnormalities of sympathetic pathway
Horners syndrome
1. Miosis2. Ptosis3. Congested conjunctiva4. Hyper or hypo hedrosis5. Heterochromia in congenital horners6. Apparent enopthalmos
Hemisphere level
• After thalamic bleed, hemispherectomy & massive infarction
• Ipsilateral
Brain stem level
• Associated with spinothalamic tract so there will be pain and temperature loss on the opposite side.
• Vascular lesions, MS, pontine gliomas and brain stem encephalitis
Associated with anhydrosis
Cervical cord level
• Associated with central cord lesions (loss of pain sensation in the arm, loss of arm reflexes and sometimes bilateral Horners)
• Anhydrosis • Causes: syringomyelia, glioma, ependymoma and cervical
trauma.
Root lesion at T1
• Pancoast syndrome ( wasting of small muscles of the hand, severe nocturnal pain in shoulder and axilla & horners syndrome) due to metastasis to apical pleura.
• Cervical rib• Avulsion of lower brachial pexus (klumpke’s paralysis)• Aneurysm of aortic arch.
Sympathetic chain
• No anhydrosis
• Due to causes in the neck• Occlusion of carotid art, dissection of carotid
art, migraine, malignancies, irradiation of neck
Pupillary abnormalities in the unconscious
• Normal• Unequal• Bilateral dilated• Bilateral pinpoint
Reaction Small (miotic) pupil Large (mydriatic) pupilsNon-reactive to light A-R pupils
Pontine hemorrhageOpiates Pilocarpine drops
1. HA pupils2. Post traumatic irridoplegia3. Atropine4. Overdosage of glutethemide,
amphetamine, cocain or derivatives
5. Poisoning: belladona, dhatura6. Brain death
Reactive to light Old ageHolmes Adie pupilHorners syndromeAnisocoriaIritis
AnxietyChildhoodPhysiological anisocoria
That’s all folks