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