BRAIN STEM, CEREBELLUM and BRAIN STEM, CEREBELLUM and NEURO-OPTHALMOLOGYNEURO-OPTHALMOLOGY

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20072007

GROSS ANATOMY GROSS ANATOMY

LATERAL VIEWLATERAL VIEW

LOCATION OF CRANIAL NERVE LOCATION OF CRANIAL NERVE NUCLEI WITHIN BRAINSTEMNUCLEI WITHIN BRAINSTEM

CRANIAL NERVE 5CRANIAL NERVE 5

Note that although all fibres enter the brainstem at the level of the pons, those concerned with pain and temperature descend as low as C3

PATHWAYS INVOLVED IN PATHWAYS INVOLVED IN HORIZONTAL GAZEHORIZONTAL GAZE

LEFT FRONTAL EYE FIELD

INTERNUCLEAR INTERNUCLEAR OPTHALMOPLEGIA ( INO)OPTHALMOPLEGIA ( INO)

THE FACIAL NERVETHE FACIAL NERVE

The Long Tracts

Note sites of decussation of major tracts :

Spinothalamic

Cuneate / Gracile

Corticospinal

Blood supply of Brainstem and Cerebellum

1) Ant. cerebral

2) Internal carotid

3) Middle cerebral

4) Post. communicating

5) Sup. cerebellar

6) Basilar

7) Ant. Inf. cerebellar

8) Vertebral

9) Ant. Spinal

10) Post. Spinal

11) Post. Inf. Cerebellar

12) Post cerebral

13) Mesencephalic

posterior

Somatotopy of cerebellumSomatotopy of cerebellumMidline lesions:

• nystagmus

•Titubation

•Trunk / gait ataxia

Hemispheric lesions:

• nystagmus

• ipsilateral limb signs

Basic Plan of Cerebellar connections

DN= Dentate nucleus

T = Thalamus

RN = Red nucleus

Each cerebellar cortex controls ipsilateral side of bodyEfferents to cortex leave cerebellum via superior cerebellar peduncle

Note: red nucleus is present in midbrain and ultimately controls contralateral half of body

DSCT= dorsal spinocerebellar tract

VSCT= ventral spinocerebellar tract

VSCT is crossed in the cord but crosses back within cerebellum

Which of the following Which of the following patients cannot have MG?patients cannot have MG?• Right eye totally paralysed, left eye moves Right eye totally paralysed, left eye moves

freely but with ptosisfreely but with ptosis• Inability of both eyes to move to left with no Inability of both eyes to move to left with no

diplopiadiplopia• Bilateral inability to look up with bilateral Bilateral inability to look up with bilateral

ptosisptosis• Left eye deviated down and laterally with Left eye deviated down and laterally with

ptosis on left and left pupil larger than rightptosis on left and left pupil larger than right

AnisocoriaAnisocoria“ “ Inequality between the 2 pupils”Inequality between the 2 pupils”

Pupils may be :Pupils may be :

- equal ( to within 1mm)- equal ( to within 1mm)- unequal due to surgery ( usually irregular)- unequal due to surgery ( usually irregular)- unequal due to neurological disease- unequal due to neurological disease

The 2 neurological causes of The 2 neurological causes of anisocoriaanisocoria1.1. One pupil too bigOne pupil too big2.2. One pupil too smallOne pupil too small

Parasympathetic---------------------------------------Sympathetic

Constricts (Ach)

III

Dilates (Nad)

Symp fibres

Anisocoria rulesAnisocoria rules1.1. Darkness exaggerates failure of Darkness exaggerates failure of

dilationdilation2.2. Bright light exaggerates failure of Bright light exaggerates failure of

constrictionconstriction3.3. If unilateral ptosis is present assume If unilateral ptosis is present assume

that the eye with the ptosis is sick!that the eye with the ptosis is sick!

Sphincter pupillae muscle

Left RAPD

AKA Marcus-Gunn pupil

For example a patient with multiple sclerosis who is suffering from acute left sided optic neuritis

Sphincter pupillae muscle

THE ENDTHE END

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