Brainstem –
The brainstem is the oldest/smallest region in the evolving brain (Often known as the `Reptilian Brain` - as it’s the major
part of present-day reptiles) – Helps in control of vegetative processes (E.g., Breathing/Heart rate/Autonomic brain +
Alertness) – Mainly concerned with fundamental needs (E.g., Survival, Physical maintenance, Dominance, Mating)
The brain then developed the neocortex in order to develop sophisticated reasoning and linguistic development
Brainstem Pathology –
Lateral Medullary Syndrome –
Thrombosis of the Vertebral/Posterior Inferior Cerebellar Artery causing ischaemia
Symptoms – Dizziness, Vomiting, Nystagmus (Vestibular Nuclei) Ataxic limbs ipsilaterally (Impaired coordination), Dysphagia
and Dysarthria
Medial Medullary Syndrome –
Thrombosis of the Medial Medullary branches of Vertebral artery or the Anterior Spinal artery which affects the pyramids,
Medial Lemniscus, and hypoglossal nerve
Symptoms – Contralateral hemiparesis, Ipsilateral lingual paralysis, Contralateral impaired Proprioception/Vibration/Touch
Locked-in Syndrome –
Bilateral damage of the medulla as a result of trauma to the Basilar artery occlusion or aneurysm rupture
Ondine`s Curse –
A syndrome of central hypoventilation caused by a lesion in medulla/trauma to cervical spine which impairs breathing so
the patient must consciously breathe
Treatment – Tracheostomy and/or mechanical ventilation
Benedikt`s Syndrome –
Involves the occlusion of the Basilar artery branches to the CN III nucleus in the midbrain which causes Complete/Partial CN
III nerve palsy and damage to the Red Nucleus leads to a contralateral tremor
Millard-Gubler Syndrome –
Involves the occlusion of the branches of Basilar artery to the Pons affecting the CN VI, VII (Abducens/Facial), Medial
Lemniscus (Control of vibration/touch/proprioception/two-point discrimination) and pyramids
Symptoms – Ipsilateral Abducens/Facial nerve palsy, Contralateral sensory deficit and Contralateral Hemiparesis/plegia
Duret Haemorrhage –
Small lineal areas of bleeding in the midbrain/upper pons due to traumatic downward displacement, 2ndary to raised
Intracranial pressure with formation of Transtentorail pressure cone involving the Cerebral Crura
Symptoms – Paralysis, Aphasic (Inability to comprehend/formulate language) but may preserve some eye/facial movement
,Brainstem Anatomy –
,Midbrain Summary –
Located between the diencephalon and Pons and is the pathways for tracts running between and higher/lower neural
centres
Has two bulging cerebral peduncles on ventral side containing descending fibres from the cerebellum (Descending
Pyramidal Tracts) whilst the Cerebral aqueduct runs through connecting the 3rd/4th Ventricles, above the Cerebral aqueduct
is the colliculi (Sup. – Controls movement in response to vision, Inf. – Controls movement in response to sound)
Pons Summary –
Located between the Midbrain and the Medulla and contains the nuclei of the Cranial Nerves V, VI, VII and VIII as well as
the Respiratory nuclei (Apneustic/Pneumotaxic centres – work with medulla to maintain respiratory rhythm)
Contains the tracts to and from the Cerebellum and forms the floor of the 4th ventricle
Medulla (Oblongata) Summary –
The most inferior part of the brainstem and becomes continuous with the Spinal Cord at the Foramen Magnum. Ventrally
has two ridges (Pyramids) which are formed by the Cerebrospinal Tracts
Has various nuclei –
• Autonomic – Cardiovascular centres (alters rate/force of contraction/vascular tone)
• Respiratory Rhythmicity Centres – Has inputs from the Pons
• Chemoreceptor trigger Zone – Emesis centre, Cough (Vagal), Sneeze, Swallow and hiccup
• CN nuclei IX, X, XI, and XII
• Nucleus gracilis
• Nucleus cuneatus
• Olivary nuclei (Sup. /Inf.)
Cranial Nerve Lesions and Symptoms –
Cranial Nerve III – Oculomotor –
Complete ptosis (drooping of eyelids), Pupillary reflex, Diplopia (Seeing double), Divergent squint, SR/IR/IO/MR Paralysis
Cranial Nerve IV – Trochlear –
Superior oblique paralysis in contralateral eye, Diplopia when looking down
Cranial Nerve V – Trigeminal (Mainly affects the Facial area)–
Motor – Loss of proprioception in Face, Mandible and Teeth (Medial Lemniscus Tract)
Sensory – Loss of Pain, Temperature and crude touch of face and nociceptive sensation from CN VII, X and XI
(Spinothalamic Tract)
Main Nuclei – Loss of light touch on Face (Medial Lemniscus Tract)
Cranial Nerve VI – Abducens –
Lateral rectus paralysis, Convergent squint, Diplopia when looking towards side of lesion
Cranial Nerve XII – Hypoglossal –
Flaccid Hemi-paralysis of tongue and deviates to affected side when protruded
, Overview of Nuclei –
• Edinger-Westphal Nucleus – Parasympathetic function
• CN V nucleus – Branchiomotor (Trigeminal nerve + Red
nuclei)
• CN VII nucleus – Branchiomotor (Facial nerve)
• Salivatory Nuclei (Inf. /Sup.) – Parasympathetic function
(Facial nerve)
• CN VIII – Somatic sensory
• Nucleus Ambiguus – Branchiomotor
• Nucleus Solitarius – Visceral sensory and CN VII (Facial nerve,
IX (Glossopharyngeal) and X (Vagus)
• Dorsal motor nucleus of Vagus – Parasympathetic function
