Department of Radiology University of California San Diego

The &

John R. Hesselink, M.D. 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 The Limbic System

Septum pellucidum

Corpus callosum Fornix Anterior commissure Mamillary Subcallosal body area Fimbria Paraterminal

Amygdala

Limbic Gyrus Intralimbic Gyrus Fornix & Inner Arc Hippocampal Anatomy

Choroid plexus Fimbria Choroidal Alveus fissure Hippocampal fissure

CA2 CA3

CA4 Temporal Dentate G horn CA1

Collateral Parahippocampal gyrus Hippocampal Anatomy

 Extension of subiculum  Sagittal plane: Head, body & tail  Coronal plane: • Cornu ammonis (CA1-4) •  Alveus and Fimbria  Temporal Lobe Anatomy

Netter, CIBA Collection Temporal Lobe Anatomy

Tien et al, Radiology 1993; 189:835

Naidich et al, Radiology 1987; 162:747 Epilepsy

- Affects 0.5 - 1.0% of population - 10 - 30% are refractory to medication

. Generalized . Partial Partial simple Partial complex Partial, but secondary generalization EPILEPSY Etiology

Hippocampal sclerosis Birth hypoxia/ischemia

Tumor Other

Hamartoma

Vascular Post traumatic

Other: Infection, migrational disorder, tuberous sclerosis, cortical dysplasia, cyst, infarct Epilepsy MR Imaging Protocol

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) 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 MR Findings

 Hippocampal atrophy

 Hyperintensity on T2 images

 Temporal horn dilatation

 Temporal lobe atrophy History: 28 y/o woman with epilepsy

709 {Page 2}

Dx: Hippocampal sclerosis History: 33 y/o female with chronic seizures

Right

Left 392 {Page 2}

Dx: Hippocampal sclerosis History: 15 y/o girl with epilepsy since age 3

Dx: Hippocampal sclerosis

753 History: 28 y/o female presented with fever & seizures

741 {Page 2) {Page 3} 7 months later

Dx: HSV encephalitis - MTS History: 34 y/o woman with Epilepsy

Dx: Malrotation hippocampus Costello’s syndrome 762 - 06335673 History: 42 y/o male 20 months s/p gamma knife for MTS

648 {Page 2}

Dx: MTS – s/p gamma knife – Decreased seizures History: 39 y/o male with two 5-minute episodes of staring

771 - 25250309 {Page 2}

Dx: Cortical dysplasia & DNET History: 14 y/o boy with partial complex seizures

306 Temporal lobe seizures {Page 2} {Page 3}

Dx: Ganglioglioma History: 45 y/o man with headache & delusional symptoms

201 Delusions {Page 2} {Page 3}

Dx: Astrocytoma (Grade 2-3) History: 7 y/o girl with seizures

Dx: Arachnoid cyst in the choroidal fissure 324 Cavernous Angioma with Hemorrhage

S 109-10 History: 44 y/o male with acute confusion & lethargy

152 Acute confusion {Page 3} {Page 4} {Page 5}

Dx: Choroid plexus / ependymal AVM - Ventricular + thalamic hemorrhage History: 49 y/o man with 2 days of visual disturbance & lightheadedness

377 {Page 2}

Dx: Hippocampal infarct History: 27 y.o. man with increasing confusion & lethargy

5 Confusion & lethargy {Page 2}

Dx: Herpes simplex encephalitis History: 16 y/o girl with epilepsy and a 22 week pregnancy – now having several seizures daily

585 {Page 2}

Dx: Seizure-related cortical edema History: 27 y/o female with seizures

760 {Page 2} {Page 3} 2 months s/p Rx with Albendazole & Dexamethasone

Dx: Cysticercosis – colloidal phase History: 39 woman with SLE on chronic immunosuppression with steroids & methotrexate

Dx: TB meningitis 701

Pachygyria / Lissencephaly

B 10 History: 55 y/o woman with refractory epilepsy for 30 years

636 {Page 2}

Dx: Polymicrogyria & septo- optic dysplasia History: 46 y/o man with seizures for many years

683 {Page 2}

Dx: Heterotopic gray matter History: 2 y/o girl with seizures

178 {Page 3} Sturge-Weber Syndrome

B 97-9 The Limbic System Related Diseases

 Developmental abnormalities

 Limbic encephalitis

 Dementia

 Neuropsychiatric disorders History: 16 y/o female with a 20 week pregnancy

Dx: Alobar holoprosencephaly 476 Septo-optic Dysplasia

B 33-5 Partial Agenesis of the

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 & • 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 , 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 Amygdala: Attaches emotional significance to sensory Hippocampus: Ventral Striatum: input Memory processing Processes rewards & Subiculum: assists with judgment and Distinguishes danger vs. behavioral decisions reward situations

Prefrontal Cortex: Regulates emotion, Raphe Nucleus: processes rewards & Produces and disperses motivation serotonin

The Bipolar Brain Depression Brain Abnormalities

 Decreased serotonin levels

 Increased ventricles & UBO’s

 Decreased frontal lobes, basal ganglia, amygdala & hippocampus

 Decreased activity of prefrontal cortex & anterior cingulate 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)