Department of Radiology University of California San Diego
The Temporal Lobe & Limbic System
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 Indusium griseum
Corpus callosum Fornix Anterior commissure Mamillary Subcallosal body area Fimbria Paraterminal gyrus Hippocampus
Amygdala Parahippocampal gyrus
Limbic Gyrus Intralimbic Gyrus Fornix & Inner Arc Hippocampal Anatomy
Choroid plexus Fimbria Choroidal Alveus fissure Hippocampal fissure
CA2 CA3
CA4 Temporal Dentate G horn Subiculum CA1
Collateral Parahippocampal gyrus 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
- 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 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 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)