Planes of the brain

• White matter": Mainly axons due to myelination (lipid/ fatty sheath)

• Grey matter: neuronal cell bodies

Main regions of the brian

Embryology

• Refer back to case 7 embryology on the formation of the spinal cord

• 

• The neural tube then splits into the main parts of the brain

• 

Rhombencephalon

• Brain stem

• Cranial nerves + normal nerves run from the medulla

• The cerebellum + pons are important in co-ordinating movements + responding to external stimuli

Cerebellum - divided i nto 3 lobes:

1. Flocculonodular lobe

   • Vestibulocerebellum/ archicerebellum

   • Regulates balance + co-ordination (oldest)

2. Posterior lobe

3. Anterior lobe

4. Contains Purkinjie + granule cells

• Areas closest to the vermis- spinocerebellum/ paleocerebellum

• Spinocerebellum: regulates body temperature + limb movement

• Laterally- neocerebellum

• Neocerebellum:

regulates planning,

sensory movement for action

Cerebellar Disorders

• Damage of the neocerebellum causes ataxic gait e.g. stroke or alcohol-related

• Cerebellum has a complex arterial supply

• Therefore, it is important in cases of stroke or vertebral/ basilar artery dissection (present with cerebellar signs

Pontine disorders

• locked-in syndrome

• Central pontine myelinolysis

• Progressive Supranuclear Palsy (Steele-Richardson-Olszewski):

  • Supranuclear ophthalmoplegia

  • Neck dystonia

  • Parkinsonism

  • Pseudobulbar palsy

  • Behavioural impairment

  • Imbalance

  • Frequently falls

Reticular formation

• Allows for communication of the brain to the rest of the body

• A hub for the synthesis of neurotransmitters and wake/sleep state

• Ascending/ descending through the brainstem

• Includes ascending reticular activating system- role in arousal

Mesencephalon

• Midbrain

• Acts as a connector between different parts of the brain

• links everything together

• Don’t worry too much about the next info

Parts of the midbrain

• Tectum (dorsal part) splits into:

• Superior colliculus- visual processing + eye movement control

• Inferior colliculus- auditory processing

Disorders of the mesencephalon

• Parkinson’s - reduction in dopaminergic neurones in substantia nigra

• Schizophrenia- increased dopamine in substantia nigra

• Multi-system atrophy- degeneration of striatum and substantia nigra

• Ventral tegmental area- primary sites of addictive drugs (heroin, cocaine, alcohol, nicotine)

Diencephalon

Contains:

• Thalamus

• Hypothalamus

• Pineal Body

• Subthalamus

• Epithalamus

• Mammillary bodies

Limbic system:

• Connects cortical control to memory / sensory/ secretory areas

• Involved in motivation, visceral processes + rewards

• Systems of emotions

• Connects a group of structures surrounding the brainstem (cingulate gyrus, hippocampus, hypothalamus + anterior thalamic nuclei)

• Connecting these structures enables cortical control of emotion + plays a role in storing memory

Telencephalon

• higher functions such as smell, memory + Intelligence

Hippocampus

• Medial temporal lobe

• Short-term memory to long term memory

• Spatial memory

• Includes dentate gyrus + granule cells - formation of new episodic memories, site of neurogenesis, affected in depression

• Alzheimer’s + dementia → hippocampal atrophy → memory symptoms

Cortex

• Memory

• attention

• Cognition

• awareness

• thought

• language

• consciousness

• 4 lobes, gyrus (fold) + sulcus

Frontal lobe

• Superior frontal gyrus = self-awareness/ laughter

• Middle frontal gyrus

• Inferior frontal gyrus = language processing, Broca’s area

• Medial frontal gyrus = executive mechanism

• Paraolfactory area= limbic

• Orbitofrontal cortex= stimulus-reward, stimulus/outcome, addiction

• Ventromedial prefrontal cortex- decision making, emotion regulation, addiction

• frontotemporal dementia/ Pick’s disease = genetic + accumulation of tau + frontal symptoms

Prefrontal cortex

• Planning + executing actions

• One of the last to develop

• lesions:

  • Dramatic changes in personality

  • Loss of spontaneity/ problems with initiating speech/ movements

  • inability to make + carry out sequences of actions/plans

Parietal lobe

• Integrates sensory information

• Dominant hemisphere lesions:

  • Dysphasia, aphasia

  • Dyscalculia- difficulty learning, doing calculations

  • Dyslexia

  • Apraxia- ability to execute or carry out skilled movements and gestures, despite having the desire and the physical ability to perform them.

  • Agnosia- inability to recognize and identify objects or persons.

  • Gerstmann syndrome- Dyscalculia, Dysphasia, finger agnosia, LR disorientation

• Non- dominant hemisphere lesions:

  • Spatial disorientation

  • Constructional apraxia

  • Dressing apraxia

  • anosognosia- unaware of their own health problems

Temporal lobe

• Transeverse temporal gyri - Heschl’s gyri

• Superior temporal gyrus= auditory context with TTG. Pricess perception of sound + apply comprehension.

• Posterior STG = wernicke’s area

• Middle temporal gyrus

• Fusiform gyrus = FACIAL RECOGNITION, synaesthesia, dyslexia, prosopagnosia

• Inferior temporal gyrus= visual object recognition

Occipital lobe

• Lingual gyrus

  • role in vision + dreaming

  • Visuo-limbic integration

  • encoding complex images

  • word processing

• Cuneus - basic visual processing

• Calcarine sulcus/fissure

  • primary visual cortex

  • takes signals from geniculate nucleus via thalamus

Tracts- only for reference

• Arcuate fasciculus- links Broca’s + Wernicks area

• Uncinate fasciculus

  • Links temporal inferior frontal gyrus + frontal lobe

  • Hippocampus + amygdala with orbitofrontal cortex

  • implicated in several psych conditions

• 2 visual streams hypothesis:

  • dorsal - where?

  • ventral- what?

Central dopamine hypothesis

• Meso-cortical pathway

• Meso-limbic pathway

• Nigrostriatal pathway

• Affected in schizophrenia + other psych disorders

• Medications for scz work on this pathway

• Side effects of these meds are linked to these pathways (e.g. cog-wheel rigidity like that seen in parkinson’s/ galactorrhea due to pituitary stimulation)

Alzheimer’s Dementia

• Microscopic accumulations of peptide amyloid-β – plaques → cause loss of synapses, then neurons.

• Progressive degeneration

• Early changes in the hippocampus (first to be damaged)

Generalised shrinking and enlarged ventricles follow

• In severe depression, the dentate gyrus don’t light up in the scans which means they don’t form many memories.

Drug misuse

• The reward system is based on dopamine.

• It activates all dopamine pathways, particularly the mesolimbic pathway.

• Dopamine is produced in the Vental Tegmental Area (VTA).

• The mesolimbic pathway links this to the Nucleus Accumbens (motivation/ reward).

• If we do something good, or use an addictive drug, this pathway is stimulated.

• The mesocortical pathway is also activated.

• This links to the Prefrontal Cortex (PFC).

• This changes how you prioritise and plan.

Disorders

Case 1- depression after frontal tumour

• 56 year old female

• Progressive apathy

• Social withdrawal

• Poor self-care for part 3 years

• Admitted to a psychiatric facility for depression

• unresponsive to antidepressants so CT was conducted

• 8cm medial bifrontal mass

• Total excision benign transitional-type meningioma → rapid improvement

• 4 months after the operation was cheerful + motivated

Case 2- Psychosis after temporal tumour

• 18-year-old female

• Referred form school to a psychosis clinic (high risk)

• 2 years of withdrawal from social activities + resent from work groups or talking in public

• 1 year later became concerned about unknown people stating + laughing at her for no reason

• Feeling the world around her has changed

• She is concerned that people are intimidating her + that there are special messages in TV for her

• She is neurologically normal + an average IQ

• Initial diagnosis: prodromal syndrome of schizophrenia but symptoms became more rapidly severe

• Routine MRI conducted

  

• Tumour in the left temporal lobe - dysembryoplastic neuroepithelial tumour (DNET)- usually benign glial neural neoplasm

• Surgically remove

• Psychotic symptoms improved with the help of other treatments- risperidone + CBT

• However, remained socially withdrawn

Case 3- bipolar effective disorder due to Wilsons disease

• Middle aged female

• Detained + admitted under section 2 of the Mental Health Act (MHA) 2007- decline in her mental state

• Initially aggressive behaviour + required restrain by the Emergency Department security + police

• Quietly spoken

• voicing paranoid persecutory delusions

• euthymic with labile affect

• alternating between anger

• tearfulness

• displaying disinhibited affection

• Doesn’t know why she was presented

• CT

  

• Hypodensity in the putamen, worse on the left

• No mass, infarct or infectious process to explain the lesions

• Consistent with the MRI from a couple of months ago which demonstrates hyperintensity of both putamina

• Associated with Wilson’s disease

• final diagnosis: psychosis secondary to neurological Wilson’s Disease

Case 4- Psychiatric syndromes associated with neurological disease

• 63-year-old male

• paranoia

• impaired anterograde memory + fatigue

• FLAIR scan shows bilateral hyperintensities in the hippocampus (arrows) → shows inflammatory process

• Blood tests revealed anti-voltage gated potassium channel antibodies