Brainstem
Anatomy aids for localization
Anatomy – Cranial Nerves
Cranial Nerves:
3, 4, (5)
5, 6, 7, 8
(5), 9, 10, 11, 12
Trigeminal Nerve (CN V)
Proprioception
Tactile
Pain and temperature
All fibers enter at Pons level but fibers conveying pain and temperature
Information descend to the spinal nucleus (down to C3)
Facial Nerve (CN VII)
Lesion proximal to the facial
nucleus will result in weakness
of the lower part of the face
(Central facial palsy)
Lesion at or distal to the facial
nucleus will result in weakness
of the upper as well as the lower
part of the face (peripheral facial
palsy)
Anatomy – Sensory vs. Motor Cranial
Nuclei
Dorsal
Spinal cord
Brain stem
Ventral
Motor Nuclei - Medial
Sensory Nuclei - Lateral
Anatomy – Long Tracts
- Base
- Spinothalamic tract (Pain and temprature)
- Pyramidal tract (corticospinal) - motor
- Medial longitudinal fasciculus (MLF) – eye movements
Pyramidal tract runs in the base:
1. Ventral to cranial nuclei in the tegmentum (T) and to spinothalamic tract.
2. In the medulla also medial to the spinothalamic tract.
Long Tracts - Decussation
Corticospinal (pyramidal)
Lower Medulla
Posterior columns
Lower Medulla
Spinothalamic Spinal cord
- Lesions at medulla and below can result in dissociated sensory syndromes
For localization combine information
Brainstem lesions result in
ipsilateral impaired cranial nerve
combined with contralateral upper
motor neuron signs
Example:
Medial midbrain (Weber) syndrome –
ipsilateral oculomoto palsy with
contralateral limb weakness
Lateral Medullary (Wallenberg) Syndrome
Causes – Vertebral artery or PICA (posterior inferior cerebellar artery) infarct
Vestibular nuclei –
Vertigo, nystagmus, nausea
Spinal tract of trigeminal nerve –
Ipsilateral facial pain and temperature
Sensation
Inferior cerebellar peduncle –
Ipsilateral cerebellar signs,
dysarthria
Sympathetic tract –
Ipsilateral Horner
Nucleus ambiguus –
Dysphonia, Dysphagia,
Vocal cord paresis
NOTICE
Pyramidal track is saved,
No significant limb paresis
Spinothalamic tract –
Contralateral pain and temperature
In limbs and trunk
Unknown origin –
Hiccups
Posterior Circulation
Few more brainstem anecdotes
Single Ocular Nerve Palsy
Oculomotor (III)
Trochlear (IV)
Abducens (VI)
Internuclear ophthalmoplegia (INO)
Disorder of conjugate lateral gaze in which the affected eye shows
impairment of adduction. The disorder is caused by injury or dysfunction
in the ipsilateral medial longitudinal fasciculus (MLF).
One-and-a-half syndrome
Lesion affecting the PPRF - paramedian pontine reticular formation (or the
abducens nucleus) and the MLF on the same side (the MLF having crossed
from the opposite side).
Locked-in syndrome
With Infarcts caudal to the mid-Pons
consciousness is fully preserved but
the only movement possible are vertical
eye movements and blinking
Bulbar symptoms
Bulbar signs - dysarthria, dysphonia, dysphagia, salivation.
Bulbar Palsy
Pseudobulbar Palsy
Lower motor neuron
Upper motor neuron due to
bilateral damage
Signs of denervation
present - tongue atrophy
and fasciculation
Inappropriate spells of crying
and laughing, Jaw jerk and
gag reflex increased
Weight loss and risk of aspiration pneumonia present in both cases
Cerebellum
Anatomy - Cerebellum
Vermis –
Gait and axial function
Each cerebellar cortex
controls ipsilateral limbs
Cerebellar hemispheres –
Limbs coordination
Flocculonodular lobe –
Eye movements and balance
Symptoms and signs of Cerebellar disease
(VANISH’D)
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Vertigo.
Ataxia - usually falls towards lesion.
Nystagmus – usually increased with gaze towards lesion.
Intention Tremor.
Scanning speech, dysarthria.
Hypotonia.
Dysdiadochokinesia and Dysmetria.
General example for an approach to
differential diagnosis of cerebellar
dysfunction
Acute
- ischemia
Focal
asymmetric - haemorrhage
Chronic
- neoplastic
- demyelination
- demyelination
Diffuse
Symmetric
- Drug intoxication:
ethanol/ BZD/ Barbs
anticonvulsants
- Wernicke encephalopathy
- alcohol
- degenerative
- hereditary
- paraneoplastic
Few more brainstem and
cerebellum anecdotes
Normal versus Pathological Nystagmus
Physiological
Never asymmetrical
Horizontal only
Pathological
Usually asymmetrical
Horizontal, vertical or
rotational
Fatigues
Usually persistent
Present only at extremes May be present at any
of horizontal gaze
position of gaze
Central versus Peripheral Vertigo
Peripheral (vestibular )
Central
Unidirectional nystagmus
Uni or Bidirectional nystagmus
Horizontal usually with rotational
component nystagmus
Horizontal, vertical or rotatory
nystagmus
May be associated with tinnitus or
hearing loss
Associated with
other cranial nerve,
cerebellar or longtract signs
No exam is complete before you
watch the patient walk!!!
Thanks,