HOW TO

LOCALISE

BRAIN STEM

LESIONS WITH

SENSORY

SYMPTOMS????

THE CURIOUS CASE OF A 62 YEAR OLD DRIVER…

H/o sudden onset of

unsteadiness of gait,tendency to fall

to right side

C/o loss of sensation in the rt half

of face & left hemitorso,dysphagia.

O/e partial

ptosis,enophthalmos, miosis of right

eye.

Cerebellar signs present

No motor loss.

ANATOMY OF BRAIN STEM

LOCALISATION OF THE LESION IS BY OBSERVING THE COMPANY THEY KEEP…

A midbrain

lesion: CN III

: ptosis, dilated

pupil, eye down and

out

: vertical gaze palsy

A lesion of the pons: CN 6 or 7

(this is a LOWER motor neurone type

lesion)

: Horizontal gaze palsy

: Unilateral facial numbness from CN 5

(results in CROSSED SENSORY

LOSS)

: Unilateral deafness

A lesion of the

medulla: bulbar palsy

: Unilateral facial numbness from

CN V

(Descending spinal tract and

nucleus)

Nystagmus :

medullo-pontine

junction.

MEDIAL LESIONS

Medial Lemniscus:

contralateral loss of vibration and

proprioception in the arm and leg

Medial longitudinal fasciculus:

ipsilateral inter-nuclear

ophthalmoplegia

Motor cranial nerve nuclei

LATERAL LESIONS

Sensory pathways.

Motor cranial nerve nuclei.

Cerebellar peduncles.

• Ataxic tremorsuperior

• General clumsinessmiddle

• Motor adaptation impaired.inferior

ptosis

BACK TO THE CASE…

Cross section of

medulla

WALLENBERGS

SYNDROME/ LATERAL

MEDULLARY SYNDROME

VENTRAL LESIONS

Descending corticospinal

pathways

LOW MEDULLARY LESIONS

Bilaterl or ipsilateral

weakness/sensory disturbance.

Main pathways decussate at this

level.

BALACLAVA HELMET DISTRIBUTION

Trigeminal sensory

fibres

Back of face-descend

more

More forward areas

of face- descend

shorter distance

MULTIPLE SCLEROSIS

Resemble trigeminal neuralgia

CEREBELLAR INVOLVEMENT

Unsteadiness of gait

Intention tremor

Nystagmus on attempted

lateral gaze

FALSE LOCALISATION SIGNS

Increased ICT – 6th CN palsy

Third nerve palsy

Tentorial herniation.

Posterior communicating

artery aneurysm

Thank you!!!