The Temporal Lobe

& Limbic System

John R. Hesselink, M.D.

Department of Radiology

University of California

San Diego

The Limbic System

The limbic lobe & its many connections

A set of 3 Arcs containing both gray

& white matter

Phylogenetically, a primitive part of brain

Central role in memory, learning, emotion

neuroendocrine function & autonomic activities

Diseases: Epilepsy, congenital anomalies,

dementias & psychiatric disorders

Limbic Gyrus Intralimbic Gyrus Fornix & Inner Arc

Indusium griseum Septum pellucidum

Corpus

callosum

Mamillary

body

Paraterminal

gyrus

Subcallosal

area

Hippocampus

Fimbria

Parahippocampal gyrus Amygdala

Fornix Anterior

commissure

The Limbic System

Choroid plexus

Hippocampal

fissure

Temporal

horn

Alveus Fimbria

CA4

CA3 CA2

Subiculum

Parahippocampal gyrus

Choroidal

fissure

CA1

Hippocampal Anatomy

Dentate G

Collateral

sulcus

Hippocampal Anatomy

Extension of subiculum

Sagittal plane: Head, body & tail

Coronal plane:

• Cornu ammonis (CA1-4)

• Dentate gyrus

Alveus and Fimbria

Amygdala

Temporal Lobe

Anatomy

Netter, CIBA Collection

Temporal Lobe

Anatomy

Tien et al, Radiology 1993; 189:835

Naidich et al, Radiology 1987; 162:747

Epilepsy

Generalized

Partial

Partial simple

Partial complex

Partial, but secondary generalization

- Affects 0.5 - 1.0% of population

- 10 - 30% are refractory to medication

EPILEPSY

Etiology

Hippocampal sclerosis

Birth hypoxia/ischemia

Tumor

Vascular Post traumatic

Hamartoma

Other

Other: Infection, migrational disorder, tuberous sclerosis,

cortical dysplasia, cyst, infarct

Epilepsy

1. Axial gradient-echo images

2. Axial FSE T2-weighted images

3. Axial FLAIR images

4. Coronal FSE T2 & FLAIR (angled perpendicular to hippocampus)

5. Gadolinium optional (new onset)

MR Imaging Protocol

Normal Hippocampus

T2-weighted Coronal

Fornix

Hippocampal Sclerosis

30 - 50% neuronal depletion

Most prominent in CA1 region of

hippocampal body

Loss of inhibitory interneurons

Synaptic reorganization

History of febrile seizures

Temporal Lobe Epilepsy

Hippocampal atrophy

Hyperintensity on T2 images

Temporal horn dilatation

Temporal lobe atrophy

MR Findings

History: 28 y/o woman with epilepsy

709

Dx: Hippocampal sclerosis

{Page 2}

History: 33 y/o female with chronic seizures

392

Right

Left

Dx: Hippocampal sclerosis

{Page 2}

Dx: Hippocampal sclerosis

History: 15 y/o girl with

epilepsy since age 3

753

History: 28 y/o female presented

with fever & seizures

741

{Page 2)

Dx: HSV encephalitis - MTS

{Page 3}

7 months later

Dx: Malrotation hippocampus

Costello’s syndrome

History: 34 y/o woman with Epilepsy

762 - 06335673

History: 42 y/o male 20 months

s/p gamma knife for MTS

648

Dx: MTS – s/p gamma knife –

Decreased seizures

{Page 2}

History: 39 y/o male with two

5-minute episodes of staring

771 - 25250309

Dx: Cortical dysplasia & DNET

{Page 2}

History: 14 y/o boy

with partial complex seizures

306

Temporal lobe seizures

{Page 2}

Dx: Ganglioglioma

{Page 3}

History: 45 y/o man with headache

& delusional symptoms

201

Delusions {Page 2}

Dx: Astrocytoma (Grade 2-3)

{Page 3}

Dx: Arachnoid cyst in the

choroidal fissure

History: 7 y/o girl with seizures

324

Cavernous Angioma

with Hemorrhage

S 109-10

History: 44 y/o male with acute

confusion & lethargy

152

Acute confusion {Page 3}

{Page 4}

Dx: Choroid plexus / ependymal AVM -

Ventricular + thalamic hemorrhage

{Page 5}

History: 49 y/o man with 2 days of visual

disturbance & lightheadedness

377

Dx: Hippocampal infarct

{Page 2}

History: 27 y.o. man with

increasing confusion & lethargy

5

Dx: Herpes simplex

encephalitis

Confusion & lethargy

{Page 2}

History: 16 y/o girl with epilepsy and a 22 week

pregnancy – now having several seizures daily

585

Dx: Seizure-related cortical edema

{Page 2}

760

History: 27 y/o female

with seizures

{Page 2}

Dx: Cysticercosis – colloidal phase

{Page 3}

2 months s/p Rx with

Albendazole & Dexamethasone

Dx: TB meningitis

History: 39 woman with SLE

on chronic immunosuppression

with steroids & methotrexate

701

Pachygyria / Lissencephaly

B 10

History: 55 y/o woman with

refractory epilepsy for 30 years

636

Dx: Polymicrogyria & septo-

optic dysplasia

{Page 2}

History: 46 y/o man with seizures for many years

683

Dx: Heterotopic gray matter

{Page 2}

History: 2 y/o girl with seizures

178

{Page 3}

Sturge-Weber Syndrome

B 97-9

The Limbic System

Developmental abnormalities

Limbic encephalitis

Dementia

Neuropsychiatric disorders

Related Diseases

Dx: Alobar holoprosencephaly

History: 16 y/o female

with a 20 week pregnancy

476

Septo-optic Dysplasia

B 33-5

Partial Agenesis

of the Corpus Callosum

B 61-2

Limbic Encephalitis

Paraneoplastic syndrome

Acts like an encephalitis

Memory loss, dementia,

involuntary movements,

& ataxia

Lacomis DL, et al. JCAT 1990; 14:115

Alzheimer’s Disease

Severe memory deficits

Path: senile plaques & neurofibrillary tangles

Hypometabolism & decreased CBF in parietal &

temporal lobes

Deficiency of cholinergic-producing neurons in the

subcallosal nuclei

Atrophy hippocampus, amygdala & entorhinal cortex

• 10 times faster than normal aging

Imaging: MRI, PET, SPECT

- MRS: Elevated myo-inositol

Alzheimer’s Disease

ADNI Study – Courtesy James Brewer, UCSD

Frontotemporal Dementia

With tau protein = Pick’s disease

Deterioration of personality,

behavior & judgment

Memory preserved until later

stages

Imaging: MRI, MRS, PET, SPECT

Neuropsychiatric Disorders

Anxiety Disorders

Schizophrenia

Affective disorders

Psychopathic disorders

Anxiety Disorders

Panic, phobias, stress disorders

Amygdala attaches emotional significance to sensory

input

Fear circuitry: Amygdala modulates neural circuitry

in orbital, ventral and prefrontal cortex, the anterior

cingulate and the entorhinal cortex

Failure of the anterior cingulate and hippocampus to

modulate the activity of the amygdala

fMRI: overactivity of the amygdala during facial

recognition tasks

Schizophrenia

Decreased anterior cingulate volume and NAA

fMRI: decreased amygdala response during facial

recognition tasks

Decreased size of hippocampus

Deficit in working memory: decreased activity in dorsolateral prefrontal cortex

Cognitive dysmetria hypothesis: disruption of the cortical-thalamic-cerebellar-cortical loops

The Bipolar Brain

Prefrontal Cortex:

Regulates emotion,

processes rewards &

motivation

Amygdala:

Attaches emotional

significance to sensory

input Ventral Striatum:

Processes rewards &

assists with judgment and

behavioral decisions

Hippocampus:

Memory processing

Subiculum:

Distinguishes danger vs.

reward situations

Raphe Nucleus:

Produces and disperses

serotonin

Depression

Decreased serotonin levels

Increased ventricles & UBO’s

Decreased frontal lobes, basal ganglia, amygdala & hippocampus

Decreased activity of prefrontal cortex & anterior cingulate

Brain Abnormalities

Severe Depression

Limbic-Cortical Dysregulation

Hypometabolism in dorsal compartment

Prefrontal cortex, anterior cingulate, inferior parietal,

striatum

Symptoms of apathy, attention deficits & psychomotor

slowing

Hypermetabolism in ventral compartment

Hypothalamus, insula, subcallosal region & brain stem

Disturbed sleep, appetite & libido

Mayberg, 1997

Psychopathic Disorders

Impulsive & aggressive behavior

Deficits in informational & emotional

processing

Malfunction of neural circuits in

prefrontal and temporal-limbic regions

(important for emotional learning)