NA II LECTURE PDF

UCL Great Ormond Street Institute of Child Health

Overview of Presentation

  • Speaker: Mr. Rory Piper, MRCS PhD, Clinical Lecturer in Neurosurgery

  • Institution: UCL Great Ormond Street Institute of Child Health

Author & Resources

  • Slide Credit/Resources:

    • Paul Johns – Professor of Neuropathology

    • Crossman and Neary, Gray’s Anatomy

    • Radiopaedia

Brain Lobes

  1. Frontal Lobe

  2. Temporal Lobe

  3. Parietal Lobe

  4. Occipital Lobe

  5. Limbic Lobe (also known as the Limbic System)

  6. Insula

  7. Central Lobe

    • This classification covers both the traditional anatomical lobes and the systems involved in emotional and cognitive processing.

Temporal Lobe Structure & Function

Seminar Contents

  • Summary of:

    • Structure

    • Function

    • Surfaces

    • Cross sections

    • Functional localization

    • Anatomical neighbors

    • Clinical correlates

    • Surgical relevance

Overview of Temporal Lobe

  • Name Origin: From the Latin word temporalis, meaning "of time".

  • Bilateral structure: Present in both hemispheres of the brain.

  • Anatomical & Functional Asymmetry: Differences observed between the left and right temporal lobes.

  • Surfaces/Cortical Anatomy:

    • Lateral Surface

    • Sylvian Surface

    • Basal (Inferior) Surface

    • Medial (‘Mesial’) Surface

  • Embryology & Histology:

    • Lateral Neocortex

    • Contention of division between temporal and limbic structures

    • Mesial Archicortex

    • White Matter Structures: Includes the arcuate fasciculus, uncinate fasciculus, inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus (ILF), anterior commissure, fornix, cingulum, and optic radiation.

Lateral Surface of Temporal Lobe

  • Major anatomical features:

    • Lateral Fissure

    • Superior Temporal Gyrus

    • Middle Temporal Gyrus

    • Inferior Temporal Gyrus

Language Areas in the Temporal Lobe

  • Wernicke’s Area: Responsible for receptive language processing.

  • Broca’s Area: Responsible for expressive language capabilities.

  • Arcuate Fasciculus: Connects Wernicke’s and Broca’s areas, essential for language conduction.

Language Lateralization

  • Incidence of Right-Hemisphere Language Dominance:

    • 4% in strong right-handed individuals

    • 15% in ambidextrous individuals

    • 27% in strong left-handed individuals

    • Source: Knecht et al., Brain, 2000.

Sylvian Surface Overview

  • Includes:

    • Frontal Pole

    • Occipital Pole

    • Transverse Temporal Gyri

    • Temporal Pole

    • Heschl's Gyrus

Coronal Structure of the Temporal Lobe

  • Key Features:

    • T1 = Superior Temporal Gyrus

    • s.t.s = Superior Temporal Sulcus

    • T2 = Middle Temporal Gyrus

    • i.t.s = Inferior Temporal Sulcus

    • T3 = Inferior Temporal Gyrus

    • o.t.s = Lateral Occipital Temporal Sulcus

    • T4 = Fusiform Gyrus

    • c.s. = Collateral Sulcus

    • T5 = Parahippocampal Gyrus

    • HF = Hippocampal Formation

Basal and Medial Surface Overview

  • Basal Surface Features:

    • Inferior Temporal Sulcus (i.t.s)

    • Lateral Occipital Temporal Sulcus (LOTS)

    • Fusiform Gyrus

    • Collateral Sulcus (CS)

    • Parahippocampal Gyrus

    • Rhinal Sulcus (RS)

    • Lingual Gyrus (LG)

  • Medial Surface Features:

    • Central Sulcus

    • Cingulate Sulcus

    • Fornix

    • Uncus

    • Parahippocampal Gyrus

    • Cingulate Gyrus

    • Calcarine Sulcus

Limbic System Overview

  • Meaning: Refers to the structures involved in emotions and memories; Etymology suggests a "border, ring, or surround".

  • Structure: A C-shaped structure encompassing the diencephalon, including telencephalic and diencephalic structures, as well as cortical, subcortical, and nucleic structures.

  • Connections: It is connected with the hypothalamus, forming an integrated system.

  • Function: Involves emotions, learning, memory, and primitive survival functions according to Ribas.

Key Structures of the Limbic System

  • Cingulate Gyrus

  • Parahippocampal Gyrus

  • Hippocampal Formation

  • Hippocampus (also called Ammon's Horn)

  • Subiculum

  • Dentate Gyrus

  • Prehippocampal Rudiment/Indusium Griseum

  • Frontal Mediobasal Cortical Area

  • Paraterminal Gyrus

  • Olfactory Cortical Areas

Limbic System Medial View

  • Structures include:

    • Cingulate Gyrus and Cingulum

    • Mammillothalamic Tract

    • Mammillary Body

    • Hippocampus and Anterior Nucleus of Thalamus

Cingulate Gyrus & Cingulum

  • Relevant in various conditions, including the discussion of bilateral cingulotomy for chronic pain (Reference: Agarwal et al., 2016).

Papez Circuit

  • Important connecting structures within the limbic system, which includes:

    • Commissure of Fornix

    • Anterior Nucleus of Thalamus

    • Mammillary Body

    • Cingulate Gyrus

    • Cingulum

    • Fornix and its components

Functions of the Hippocampus

  • Responsible for:

    • Episodic Memory

    • Spatial Navigation

Additional Features of the Hippocampus

  • Consists of:

    • Cornu Ammonis (divided into subfields 1, 2, 3, & 4)

    • Dentate Gyrus

    • Subiculum

    • Composed of three cortical layers as it is classified as allocortex (archicortex).

Dense Anterograde Amnesia

  • Episodic Memory: Significant impairment.

  • Spatial Navigation: Affected, with context-dependent memory being variable.

  • Implicit Memory: Mainly preserved, meaning procedural learning and conditioning remain intact.

  • Functional implications include temporary storage of new memories and consolidation into long-term memory.

Fornix Structure

  • Components interacting with other limbic structures, similar functions as established in connections above.

Mammillary Body Relationship

  • Structures and connections similar to those described for the fornix, significant in memory processes.

Amygdala as Part of Limbic System

  • Klüver-Bucy Syndrome: Neural and behavioral changes due to bilateral temporal lobe lobectomies involving:

    • Memory changes

    • Social and sexual behavior changes

    • Symptoms include hyperphagia (compulsive overeating), hyperorality (examining objects by putting them in the mouth), and hypersexuality (increased sex drive), and various paraphilias.

Limbic System Integration

  • Connections to multiple cortical regions as well as autonomic nervous systems, forming essential pathways for emotional and behavioral responses. Key components include:

    • Orbitofrontal cortex

    • Inferior temporal neocortex

    • Ventral pathways including amygdala and cingulum

White Matter Connections

  • Various white matter pathways contribute to connections between lobe structures and functional integration, including:

    • Cingulum

    • Uncinate fasciculus

    • Arcuate fasciculus

    • Anterior and Inferior Longitudinal Fasciculi

    • Fornix

Temporal Lobe Epilepsy Surgery

  • Discusses the surgical interventions in aspects of temporal lobe epilepsy and relationships with the superior temporal lobe and seizure-onset zones, applicable methodologies include:

    • TLFB (Temporal Lobe Functional Bipolar) and ATLR (Anterior Temporal Lobectomy) techniques.

Temporal Lobe Pathologies & Seizures

  • Mesial Temporal Lobe Epilepsy (MTLE)

  • Neocortical Temporal Lobe Epilepsy (TLE)

    • Predominant pathologies include:

      • Hippocampal sclerosis

      • Low-grade epilepsy-associated neuroepithelial tumors

      • Focal cortical dysplasia (FCD)

      • Vascular malformations

      • Encephalitis

    • Typical semiology involves auras, autonomic features, and varying duration and characteristics of seizures.

UCL Great Ormond Street Institute of Child Health

  • Speaker: Mr. Rory Piper, MRCS PhD, Clinical Lecturer in Neurosurgery

  • Resources: Professor Paul Johns (Neuropathology), Crossman and Neary, Gray’s Anatomy, and Radiopaedia.

1. Enhanced Overview of Brain Lobes

  1. Frontal Lobe: Governing executive functions, motor control (Primary Motor Cortex), and personality.

  2. Temporal Lobe: Primary site for auditory processing, language comprehension, and memory consolidation.

  3. Parietal Lobe: Responsible for somatosensory integration, visuospatial processing, and symbolic representation.

  4. Occipital Lobe: Dedicated to primary visual processing (V1) and interpretation.

  5. Limbic Lobe (Limbic System): Involved in emotional regulation, motivation, and the formation of new memories.

  6. Insula: Located deep within the lateral fissure; involved in interoception, emotional awareness, and gustatory processing.

  7. Central Lobe: Refers to the peri-rolandic area, integrating motor and sensory feedback for refined movement.

2. Temporal Lobe Detail: Structure & Surfaces

  • Anatomical Nomenclature: Derived from the Latin temporalis ("of time"), reflecting that gray hair associated with aging typically appears first at the temples.

  • Physiological Asymmetry: While anatomical structures appear bilateral, function is highly lateralized; the left hemisphere is dominant for language in approximately 96\% of right-handed individuals.

  • Cortical Surfaces:

    • Lateral Surface: Contains the Superior (T1), Middle (T2), and Inferior (T3) temporal gyri, separated by the superior and inferior temporal sulci.

    • Sylvian Surface: The upper surface of the temporal lobe hidden within the Sylvian fissure; home to Heschl’s Gyri (Primary Auditory Cortex, Broadmann Areas 41 and 42).

    • Basal (Inferior) Surface: Rests on the tentorium cerebelli; includes the Fusiform Gyrus (T4), critical for facial and object recognition (lesions lead to Prosopagnosia).

    • Medial (Mesial) Surface: Part of the phylogenetically older archicortex; includes the Hippocampal Formation and Parahippocampal Gyrus (T5).

3. Language Processing and Lateralization

  • Wernicke’s Area: Located in the posterior portion of the superior temporal gyrus (BA 22) in the dominant hemisphere. It is vital for receptive language; damage results in "Fluent Aphasia."

  • Broca’s Area: Located in the inferior frontal gyrus (BA 44, 45). Damage leads to "Expressive Aphasia," where comprehension is intact but speech production is effortful.

  • Arcuate Fasciculus: A large bundle of white matter axons connecting Wernicke’s and Broca’s areas. Interruption leads to Conduction Aphasia, where the patient cannot repeat phrases.

  • Lateralization Statistics:

    • Strong Right-handed: 4\% Right-hemisphere dominance.

    • Ambidextrous: 15\% Right-hemisphere dominance.

    • Strong Left-handed: 27\% Right-hemisphere dominance.

4. The Limbic System: Structure and Circuitry

  • Definition: A group of structures surrounding the brainstem involved in the "four F's": Feeding, Fighting, Fleeing, and Sexual behavior.

  • The Papez Circuit: A fundamental pathway for memory and emotional expression:

    • \text{Hippocampus} \rightarrow \text{Fornix} \rightarrow \text{Mammillary Bodies} \rightarrow \text{Anterior Thalamic Nucleus} \rightarrow \text{Cingulate Gyrus} \rightarrow \text{Parahippocampal Gyrus} \rightarrow \text{Hippocampus}.

  • Cingulate Gyrus: Specifically the anterior cingulate, it is involved in the emotional response to pain and error detection.

5. Hippocampal Formation and Memory

  • Anatomic Subfields: Consists of the Cornu Ammonis (CA1, CA2, CA3, CA4), the Dentate Gyrus, and the Subiculum.

  • Histology: Classified as Allocortex, consisting of only 3 cellular layers compared to the 6 layers of the Neocortex.

  • Functions:

    • Episodic Memory: Recording specific events and their context.

    • Spatial Navigation: Mediated by "place cells" that map the environment.

  • Clinical Relevance: Dense Anterograde Amnesia:

    • Occurs with bilateral mesial temporal damage (e.g., Patient HM).

    • Patients cannot form new explicit memories but often retain Implicit (Procedural) Memory, allowing them to learn new motor tasks without conscious recall of the training.

6. The Amygdala and Klüver-Bucy Syndrome

  • Amygdala: Responsible for fear conditioning and assigning emotional value to stimuli.

  • Klüver-Bucy Syndrome: Arises from bilateral anterior temporal lobe damage, presenting with:

    • Placidity: A profound loss of fear and anger response.

    • Hyperorality: A compulsion to explore objects by mouth.

    • Hyperphagia: Compulsive overeating (Bulimia).

    • Hypersexuality: Heightened and often inappropriate sexual behavior.

7. Clinical Pathologies and Epilepsy Surgery

  • Mesial Temporal Lobe Epilepsy (MTLE): The most prevalent form of refractory focal epilepsy.

  • Pathological Findings:

    • Hippocampal Sclerosis: Neuronal loss and gliosis, particularly in the CA1 sector (Sommer's Sector), which is highly vulnerable to hypoxia.

    • Focal Cortical Dysplasia (FCD): Abnormalities in cortical development.

  • Seizure Semiology: Often starts with "auras," such as a rising epigastric sensation, olfactory hallucinations (uncinate fits), or intense déjà vu.

  • Surgical Relevance:

    • Standard Anterior Temporal Lobectomy (ATLR): Removal of the temporal pole and mesial structures.

    • Selective Amygdalohippocampectomy: Reserved for cases where the seizure focus is strictly limited to the mesial structures, aiming to spare the lateral temporal neocortex.