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TEMPORAL LOBE ANATOMY,FUNCTION DISORDER,MRI FINDING
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TEMPORAL LOBE
•H.H. –40 years old, successful lawyer–Left wife of 15 years to join a religious group–Experienced a seizure and a left temporal lobe tumor was found –Tumor removed and H.H. was able to return to his job–Left with word-finding difficulties
• ANATOMY(parts)
• FUNCTIONAL AREAS
• LOOPS & PATHWAYS
• FUNCTIONS
• DISORDERS
3
0VERVIEW
ANATOMY OF TEMPORAL LOBE
Directionally, the temporal lobes are anterior to the occipital lobes, inferior to the frontal lobes and parietal lobes, and lateral to the Fissure of Sylvius, also known the lateral sulcus
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Occurs only in primates and is largest in man
Approximately 17% of the volume of cerebral cortex16% in the right and 17% in the left hemisphere
Temporal cortex includes auditory, olfactory, vestibular, and visual senses ,prception of spoken and written language
Addition to cortex, its contains white matter, part of the lateral ventricle, the tail of the caudate nucleus, the stria terminalis, the hippocampal formation, and the amygdala
• SUPERIOR AND INFERIOR TEMPORAL SULCI DIVIDE TEMPORAL LOBE INTO 3 LOBES
• SUPERIOR TEMPORAL LOBE
• MIDDLE TEMPORAL LOBE
• INFERIOR TEMPORAL LOBE
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Involves areas 41,42,22Primary auditory area (area 41)On the left side of the brain this area helps
withgeneration and understanding of individual
words. On the right side of the brain it helps tell the
differencebetween melody, pitch, and sound intensity
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SUPERIOR TEMPORAL LOBE
The region encompasses most of the lateral temporal
cortex, a region believed to play a part in auditory
processing and languageLanguage function is left lateralized in most
individualsBrodmann area 21
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MIDDLE TEMPORAL LOBE
Its corresponds to the inferior temporal gyrus. Brodmann area 20The region encompasses most of the ventraltemporal cortex, a region believed to play a partin high-level visual processing and recognitionmemory
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INFERIOR TEMPORAL LOBE
Auditory areas Brodmann’s areas 41,42, and 22
Ventral Stream of Visual Information -Inferotemporal cortex or TE, Brodmann’s areas 20, 21,37, and 38
Relations of the temporal lobe coronal section passing through the temporal pole, anterior to the amygdala, hippocampus, and temporal horn
Relations of the temporal lobe coronal section passing through the amygdala and the head of the hippocampus
Relations of the temporal lobe, horizontal section in the plane of the pituitary gland
The hippocampus is a scrolled structure located in the medial temporallobe The hippocampus can be divided into at least five different areas.The dentate gyrus is the dense dark layer of cells at the "tip" of thehippocampus. Areas CA3 and CA1 are more diffuse; the small CA2 ishard to distinguish between them. (CA stands for cornu ammonis,from its ram's horn shape.) The subiculum sits at the base of the hippocampus, and is continuouswith entorhinal cortex, which is part of the parahippocampal gyrus.
The Hippocampus
Dentate gyrus represents the free edge of the pallium and associated white matter, the alveus, fimbria, and fornix.
The cortex adjacent to the hippocampus is known as the entorhinal area, it present along the whole length of the parahippocampal gyrus
The hippocampal formation has indirect afferent connections from the whole of the cerebral cortex, funneled through the adjacent temporal cortex and the subiculum
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(1) inputs from the entorhinal region, which include the perforant and alvear pathways; (2) internal circuitry, which includes the connections of the mossy fibers and Schaffer collaterals; and (3) efferent projections of the hippocampal formation through the fimbria-fornix system of fibers. CA1-CA4 denote the four sectors of the hippocampus
The hippocampus is vulnerable to ischemia, which is any obstruction of blood flow or oxygen deprivation, Alzheimer's disease, and epilepsy.
These diseases selectively attack CA1, which effectively cuts through the hippocampal circuit
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Diseases of the Hippocampus
Amygdala
Amygdala
Amygdala located in the medial part of the temporal pole, anterior to and partly overlapping the hippocampal head
Its receives fibres of the olfactory tract
The ambient and semilunar gyri consist of periamygdaloid cortex receives fibres from the olfactory tract
The larger lateral part of the amygdala, like the hippocampal formation, receives direct and indirect input from most of the cerebral cortex
Inputs: The association areas of visual, auditory, and somatoSensory cortices are the main inputs to the amygdala
Outputs: The main outputs of the amygdala are to theHypothalamus and brainstem autonomic centers, including thevagal nuclei and the sympathetic neuronsThe amygdala is also involved with mood and the consciousemotional response to an eventThe amygdala is also extensively interconnected with frontalcortex, medio dorsal thalamus, and the medial striatum
Amygdala
The deep group, which includes thelateral, basal, accessory basal
nucleic
Func: collects input from sensorycortex.
The more dorsal group, whichincludes the central & medial
nuclei
Func: receives projections from thedeep group and sends the signal
outto autonomic centers.
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The amygdala is the heart of the emotional system. It
processes and interprets all sensory data
It modulates the flow of emotional information between
the cerebral cortex and the hypothalamus, and in doing
that, it modulates autonomic, endocrine, and affective
responses
Lesions in amygdala lead to-- agitation, irritability,
anxiety, mood disorders, paranoia, and psychosis
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Kluver-Bucy syndrome results due to a bilateral destruction ofthe amygdaloid body and inferior temporal cortex It is characterized by Visual agnosiaPlacidityHypermetamorphosisHyperorality Hypersexuality causes: cerebral trauma; infections including herpes andother encephalitides; Alzheimer's disease and other dementias,Niemann-Pick disease and cerebrovascular disease
Kluver-Bucy syndrome
White MatterSubcortical white matter comprises three populations of axons Association fibres connect cortical areas within the same cerebral hemispherelargest bundle is the arcuate fasciculusbetween frontal cortex, including Broca’s expressive speech area, and Wernicke’s receptive language area in the posterior part of the superior temporal gyrus. The condition of conduction aphasia is traditionally attributed to a destructive lesion that interrupts the arcuate fasciculusAnother frontotemporal association bundle is the uncinate fasciculus hook like shape Visual association cortex extends from the occipital lobe to the middle and inferior temporal and fusiform gyri
Commissural fibres connect mainly but not exclusively symmetrical cortical areas Largest group of commissural fibres is the corpus callosum Projection fibres connect cortical areas with subcortical nuclei of grey matter
Its afferent to the temporal cortex include medial geniculate body to the primary auditory area
Connected with the amygdala, hypothalamus, hippocampal formation, and parahippocampal gyrus
Thalamocortical pathway that passes through the temporal lobe is Meyer’s loop of the geniculocalcarine tract
This loop carries signals derived from the upper quadrants of the contralateral visual fields to the corresponding primary visual cortex of the anterior half of the inferior bank of the calcarine sulcus
FUNCTIONAL AREAS OF TEMPORAL LOBE
AUDITORY – primary & Association
OLFACTORY - primary & Association
VISUAL (Recognition & association)
MEMORY
EMOTIONAL & SOCIAL
Link past and present sensory and emotional experiences into a continuous self
LANGUAGE AREAS Wernicke's area is found in posterior temporal lobe of onehemisphere (usually the left),called the "speech area, " Wernicke'sarea surrounds& encompasses part of the auditory associationArea
AFFECTIVE LANGUAGE AREAS Involved in the nonverbal emotional components ,present non dominanthemisphere opposite Brocas's and Wernickes's areasThese "mirror images" allow tone of our voice and our gestures toexpress our emotions when we speak, and permit us to comprehendthe emotional content of what we hear Lesions to this cause aprosodia, in which speech is flat and
emotionsess,lacking the intonations that modify the meaning of our spoken words
LANGUAGE & COMPREHENSION
PRIMARY AUDITORY AREA (area 41) Essential to detect changes in frequency , & to know thedirection from which sounds originate.
AUDITORY ASSOCIATION AREA (area 42)
HIGHER AUDITORY ASSOCIATION AREA (area 22)
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AUDITORY SENSES
Processing of our recognition of objects occurs in a path on the lower, dorsal stream in the temporal lobe; here you find areas sensitive to faces vs. objects,
Area MT (right) performs processing on motion. Subjects without an area MT describe seeing motion as discontinuous pictures – eg. having to rely on sound before crossing a street
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VISUAL SENSES
OLFACTORY SENSES
The rightmost green spots are the location in cortex where smell is processed
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The sensation of taste is
processed in insular cortex
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GUSTATORY SENSES
connections of the Temporal Lobes
Five main types:Hierarchical sensory pathwayDorsal auditory pathwayPolymodal pathwayMedial (mesial) temporal pathwayFrontal lobe projection
Hierarchical sensory pathway connections from primary(sensory neuron) and secondary
auditory and visual cortical
through the lateral temporal cortex
terminate in the temporal pole
visual travels inferior temporal gyrus auditory travels e suprior temporal gyrusMajor destinations:amygdala and hippocampusThis results in the integration of information into:
memory, retrieval of stored information, emotional tone
Ultimate effect stimulus recognitionThe familiar conscious experience of knowing,
assimilating, and feeling
Dorsal auditory pathway
Forms important functional connections with the posterior parietal cortex
Enables location of sounds in space Promotes orienting and initiation of movements
relative to sound location
Polymodal Pathway connections emerging from the auditory and visual
hierarchical pathways Directed towards the neurons enfolded within the
superior temporal sulcus Polymodal nature of neurons Assigns stimuli to specific category of classes,
linked to and can be retrieved by memory
Medial Temporal Projection
Medial Temporal Projection Projections from auditory and visual areas into the
limbic regions E.g., amygdala and hippocampus Directions of projectionsPeripheral cortex entorhinalcortex
amygdala/hippocampus Perforant pathway forms the main projection to the hippocampus Damage in this region severely affects memory
formation
Medial Temporal Projection
Frontal-lobe Projection
Neurons from the temporal lobe have strong connections with the frontal lobe
Posterior temporal cortex Projects to the dorsolateral prefrontal
cortex anterior temporal cortex Projects to the orbital frontal cortex Damage leads to terrible life decisions
Frontal-lobe Projection
Frontal-lobe Projection
The prefrontal cortex (PFC) divided into anterior (APFC, Brodmann area (BA) 10), dorsolateral (DLPFC, BA 46 and 9), ventrolateral (VLPFC, BA 44, 45 and 47) and medial (MPFC, BA 25 and 32) regions BAs 11, 12 and 14 are commonly referred to as orbitofrontal cortexThe medial temporal lobe comprises the hippocampus and amygdala, as well as the entorhinal, perirhinal and parahippocampal neocortical regions.There are large cortico-cortical direct reciprocal connections between the PFC and the medial temporal lobe, passing through the uncinate fascicle, anterior temporal stem and anterior corpus callosum. The orbitofrontal and dorsolateral cortices have strong reciprocal connections with the perirhinal and entorhinal corticesUnidirectional projections exist from the CA1 field to the caudal region of MPFCThe subicular complex and neocortical medial temporal regions have reciprocal connections with caudal MPFC
Arterial Blood Supply and Venous DrainageThe temporal lobe receives blood from both the carotid and the
vertebrobasilar systems.
Anterior choroidal artery are the anterior end of the parahippocampal
gyrus, the uncus, the amygdala, and the choroid plexus in the temporal
horn of the lateral ventricle
Middle cerebral artery giving off branches that supply the cortex of
the superior and middle temporal gyri and the temporal pole.
Posterior cerebral artery gives off two to four temporal branches,
before it divides into the calcarine and parieto-occipital arteries, which
supply the occipital lobe.
The temporal branches of the posterior cerebral artery supply the
inferior surface of most of the temporal lobe, but not the temporal pole.
The venous drainage of the temporal cortex
Venous drainage Temporal cortex and white matter into the superficial middle cerebral vein,in the cistern of the lateral sulcus and inferior anastomotic vein (vein of Labbé)Interior of the lobe, including amygdala, hippocampus, and fornix, flows into the posterior choroidal vein. The left and right internal cerebral veins joined by the basal veins and unite to form the great cerebral vein, a midline structure that continues into the straight sinus. The basal vein (vein of Rosenthal), which carries blood from the cortex and the interior of the frontal lobe, traverses the subarachnoid space in the cisterna ambiens, medial to the temporal lobe.
Venous drainage
Venous drainage
Processing auditory input ◦ sends ventral and dorsal streams (object identification and for
movement planning)
Visual object recognition◦ Ventral visual stream
Biological motion perception◦ Superior Temporal Sulcus
Long-term storage of information◦ Memory (limbic system, hippocampus)
Temporal Lobe Function
Sensory ProcessesIdentification and Categorization of StimuliCross-Modal Matching
Process of matching visual and auditory information
Affective ResponsesEmotional response is associated with a particular stimulus
Spatial NavigationHippocampus – Spatial Memory
Temporal Lobe Function
Special face processing pathway
Faces
Asymmetry of Temporal Lobe Function
Left temporal lobeVerbal memory Speech processing
Right temporal lobeNonverbal memoryMusical processingFacial processing
DISORDERS OF TEMPORAL LOBE
Symptoms of Temporal-Lobe Lesions
Disturbance of auditory sensation and perceptionDisturbance of selective attention of auditory and visual inputDisorders of visual perceptionImpaired organization and categorization of verbal materialDisturbance of language comprehensionImpaired long-term memoryAltered personality and affective behaviourAltered sexual behaviour
8 principal symptoms of temporal lobe damage
Disorders of auditory perception:Lesions of the left superior temporal gyrus produce problems ofspeech perception with difficulty in discriminating speech and thetemporal order of sounds is impaired
Lesions of the right superior temporal gyrus can produce disorders ofperception of music with inability to discriminate melodies and produceprosody
The inferior temporal cortex is responsible for visual perception andlesions produce inability to recognise faces, called prosopagnosia.
There may be disturbance of visual and auditory input selection. Thispresents as impairment of short term memory, also called workingmemory and judgement about the recency of events.
Manifestations of temporal lobe lesions
Disorders of memory The medial and inferior temporal cortex and hippocampus are
responsible for memory. There is complete anterograde amnesia following bilateral removal of
medial temporal lobes, including hippocampus & amygdala. The left side is responsible for verbal material and the right for non-
verbal memory such as faces, tunes and drawings.
• Temporal lobe personality. There is egocentricity, pedantic speech, perseveration of speech, paranoia, religious preoccupations and a tendency to aggressive outbursts, especially after right temporal lobectomy
• temporal lobe lesions can present with visual field defects in the form of superior quadrant loss, sometimes called the "pie in the sky defect"
• Stroke normally reduces libido but temporal lobe lesions can increase it
• Any disturbance in the comprehension or expression of language caused by a brain lesion.
• NONFLUENT APHASIA, i.e. in lesion to Broca's area results in slow speech, difficulty in choosing words, or use of words that only approximate the correct word.e.g., a person may say "tssair" when asked to identify a picture of a chair.
• A lesion to Wernicke's area may result in FLUENT APHASIA, in which a person speaks normally, and sometimes excessively, but uses jargon and invented words, that make little sense (e.g., "choss" for chair). The person also fails to comprehend written and spoken words.
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APHASIA
Middle cerebral artery in farct:Aphasia or non-dominant hemisphere findings depending onthe side.“Partial” middle cerebral artery syndromes, almostalways of embolic origin, may include a) sensorimotor paresiswith little aphasia b) conduction aphasia c) Wernicke’s
aphasiawithout hemiparesis
Wernicke's aphasia, caused by occlusion of the lower divisionof the MCA bifurcation or one of its branchesThe infarct responsible for a classic Wernicke's aphasiaincludes the dominant posterior temporal, inferior parietal,
andlateral temporo-occipital regions
Posterior cerebral artery syndrome:
Recent memory loss may be present (involvement of hippocampus) 68
CVA-TEMPORAL LOBE
Bilateral temporal lobe hyperintensity
Infective diseases (herpes simplex virus, congenital cytomegalovirus infection)Epileptic syndrome (mesial temporal sclerosis) Neurodegenerative disorders (Alzheimer's disease, frontotemporal dementia, Type 1 myotonic dystrophy)Neoplastic conditions (gliomatosis cerebri)Metabolic disorders (mitochondrial encephalopathy, lactic acidosis and stroke-like episodes, Wilson's disease, hyperammonemia) Dysmyelinating disease (megalencephalic leukoencephalopathy with subcortical cysts)Vascular (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy) Paraneoplastic (limbic encephalitis) disorders
Diagnosis (n) Percentage of total cases (n=65) Age or age range (years) Sex distribution
Infective diseases
Herpes encephalitis (15) 23 34–55 10M, 5F
Congenital CMV infection (2) 3 8–11 1M, 1F
Epileptic syndrome
Mesial temporal sclerosis (10) 15.3 8–27 6M, 4F
Neurodegenerative
Alzheimer's disease (7) 10.7 58–65 5M, 2F
Frontotemporal dementia (2) 3 61–64 2F
Myotonic dystrophy (1) 1.5 27 1M
Neoplastic
Gliomatosis cerebri (9) 13.8 33–64 6M, 3F
Metabolic
MELAS (7) 10.7 10–22 5M, 2F
Wilson's disease (1) 1.5 10 1M
Hyperammonemia (1) 1.5 61 1F
Dysmyelinating disease
MLC (6) 9.2 6–20 5M, 1F
Vascular
CADASIL (2) 3 31–35 1M, 1F
Paraneoplastic disorder
Limbic encephalitis (2) 3 25–32 2M
CADASIL, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy; CMV, cytomegalovirus; F, female; M, male; MELAS, mitochondrial encephalopathy, lactic acidosis and stroke-like episodes; MLC, megalencephalic leukoencephalopathy with subcortical cysts.
The clinical features, location and distribution of temporal lobe hyperintensity, additional and advanced MRI findings with relevant laboratory results ↓, decreased; ↑, elevated; −, negative; +, positive; A, anterior; CADASIL, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy; Cho, choline; CMV, cytomegalovirus; CPS, complex partial seizure; CSF, cerebrospinal fluid; DWI, diffusion-weighted imaging; EC, external capsule; EEG, electroencephalogram; Gd, gadolinium; GM, grey matter; HSV, herpes simplex virus; L, lateral; Lac, lactate; LOC, loss of consciousness; M, medial; MELAS, mitochondrial encephalopathy, lactic acidosis and stroke-like episodes; ML, myoinositol; MLC, megalencephalic leukoencephalopathy with subcortical cysts; MRS, MR spectroscopy; NA, not applicable; NAA, N-acetylaspartate; ND, not done; P, posterior; R, restriction; S. no., serial number; SWI, susceptibility-weighted imaging; WM, white matter; VR, Virchow–Robin spaces.
Bilateral temporal lobe hyperintensity Advanced MRI findings
S. no.
DiagnosisClinical features
Lobe GM WM Additional MRI findings DWISWI
MRSGd-enhancement
Laboratory result
1Herpes encephalitis
Fever, seizure, altered sensorium
A, M + −Orbital gyri involvement, gyriform haemorrhages
R + ND GyriformHSV antibodies in CSF
2Mesial temporal sclerosis
Complex partial seizure
M + +Hippocampal, mamillary body, fornix and collateral WM atrophy
− − ND NDTemporal lobe localisation on EEG
3Gliomatosis cerebri
Headache, recurrent seizures
A, M + +Expansion of parenchyma, multilobar involvement
− − ↑MLAbsent / patchy
Non-contributory
4 MELASEpisodes of LOC, seizure
P, M + +Fleeting hyperintensity, basal ganglia involvement
R − ↑lac Patchy↑Serum and CSF lactate
5Alzheimer's disease
Personality changes, memory loss
A, M − +Hippocampal atrophy, enlarged parahippocampal fissures
− − ↑ML − Non-contributory
6 MLCDevelopmental delay, seizure
Whole − +Temporal lobe cysts, subcortical WM, external capsule
− −↓NAA ↑cho
− Non-contributory
7Congenital CMV
Seizure P − +Periventricular cysts, pachygyria-agyria complex
− − ND − Non-contributory
8 CADASILMigraine, hemisensory loss
A, M − +
Lacunar infarcts, subcortical WM, external capsule and insula
− − ND −Non-contributory
9Frontotemporal dementia
Dementia A,M − +Fronto-temporal atrophy
− − ↓NAA ↑cho −Non-contributory
10Limbic encephalitis
Memory disturbance
M + −Cingulate gyrus, subfrontal cortex and inferior frontal WM
− − ND −
Pleocytosis, lymphoma antibodies in CSF
11 HyperammonemiaConfusion, altered sensorium
A + −Posterior cingulate gyrus
R − ND ND↑Blood ammonia
12 Wilson's disease
Weakness, extrapyramidal symptoms
A, P, L + +Fronto-parietal lobes, dorsal midbrain, deep grey nuclei
R − ND −↑Serum and urine copper, ↓ceruloplasmin
13Myotonic dystrophy
Developmental delay, facial and distal limb weakness
A − +Periventricular and deep WM, prominent VR spaces
− − ND ND
Myotonic discharges in electromyography
A 34-year-old male with herpes encephalitis (a) Coronal T2weighted image shows bilateral symmetric cortical swelling and hyperintensity involving the anteromedial temporal lobes including the insular cortex (white arrows) with characteristic sparing of basal ganglia (open arrows). (b) AxialT2 weighted image shows additional involvement of orbital gyri (black arrows). (c) Axial diffusion-weighted image depicts restricted diffusion in the involved areas (white arrows).
A 46-year-old male with herpes encephalitis (a) Axial susceptibility-weighted image demonstrates haemorrhages (black arrows) in both temporal lobes. (b) Axial T1weighted post-gadolinium image shows gyriform enhancement (white arrows) in the involved temporal lobes.
An 11-year-old female with cytomegalovirus infection(a) Axial fluid-attenuated inversion-recovery image shows bilateral periventricular cysts with gliosis of white matter (white arrows) in both temporal lobes. (b) Axial T2weighted image demonstrates gyral abnormality in the form of pachygyria–agyria complex (open arrows) bilaterally involving the temporo-occipital lobes in addition to the periventricular cysts (white arrows). Combination of these imaging findings along with periventricular calcifications are in favour of congenital cytomegalovirus infection
A 17-year-old male with complex partial seizure(a) Oblique coronal fluid-attenuated inversion-recovery image reveals bilateral hippocampal atrophy, hyperintensity indicating gliosis (white arrows) with loss of internal architecture consistent with a diagnosis of bilateral mesial temporal sclerosis. (b) Oblique coronalT1 weighted image demonstrates bilateral mamillary body atrophy (white arrows).
A 64-year-old male with memory loss and personality changes (a) Axial fluid-attenuated inversion-recovery image shows hyperintensity in both anteromedial temporal lobes (white arrows). (b) Axial T2weighted and (c) coronal T1weighted images depict marked atrophy of temporal lobes with preferential volume loss of hippocampi and parahippocampi gyri and corresponding enlargement of parahippocampal fissures including choroidal (downwards arrows on c) and hippocampal fissures (black arrows), and temporal horns (white arrow). Temporal lobe hyperintensity indicates non-specific gliosis because of marked atrophy; however, the selective mesial temporal atrophy with enlarged parahippocampal fissures are diagnostic of Alzheimer's disease
A 64-year-old female with frontotemporal dementia(a) AxialT2 weighted image shows hyperintensity with volume loss in bilateral temporal lobes (black arrows). (b) Axial fluid-attenuated inversion-recovery image demonstrates predominate volume loss in both frontal and temporal lobes with associated increased signal in white matter indicating underlying gliosis (white arrows)
A 34-year-old male with myotonic dystrophy Type 1 (a) Axial fluid-attenuated inversion-recovery image shows bilateral anterior temporal white matter hyperintensity (black arrows). (b) Coronal T2weighted image shows hyperintensity in periventricular white matter (white arrow) and prominent perivascular spaces (open arrows) disproportionate to the age.
A 61-year-old male with gliomatosis cerebri (a) Axial T2weighted image demonstrates cortical expansion and hyperintensity (white arrows) in both medial temporal lobes. (b) Axial T2 weighted image shows multifocal brain parenchymal involvement with expansion and relative preservation of architecture. Involvement of frontotemporal lobes (white arrows), basal ganglia (open arrows) and thalami (black arrows) are seen. (c) MR spectroscopy shows markedly elevated myoinositol peak at 3.45 parts per million.
A 17-year-old male with mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS)(a) Axial fluid-attenuated inversion-recovery (FLAIR) image shows bilateral asymmetric cortical and subcortical temporal lobe hyperintensity (white arrows), right more than the left and (b) axial FLAIR image 4 months later shows resolution of previous hyperintensity and new area of involvement on left side (white arrow) indicating the fleeting nature of the lesions. (c) MR spectroscopy demonstrates elevated lactate peak at 1.3 parts per million. These findings are consistent with a diagnosis of MELAS
A 61-year-old female with hyperammonemic encephalopathy. Axial fluid-attenuated inversion-recovery images show (a) bilateral peripheral cortical temporal lobe (white arrows) and (b) right posterior cingulate gyrus (open arrow) hyperintensity. Diffusion-weighted images show corresponding restricted diffusion (white arrows) in (c) the bilateral peripheral cortical temporal lobe and (d) the right posterior cingulate gyrus. The typical distribution of lesions with elevated blood ammonia level suggests this diagnosis.
A 10-year-old male with Wilson's disease. (a) Axial T2weighted and (b) fluid-attenuated inversion-recovery images demonstrate bilateral extensive cortical and subcortical temporal lobe hyperintensity (white arrows), dorsal midbrain involvement (open arrow), bilateral symmetric basal ganglia (yellow arrows) and anterolateral thalamic (black arrows) hyperintensity. Extensive grey and white matter lesions are less frequently in Wilson's disease however concomitant basal ganglia, thalamic and dorsal brainstem abnormalities point to the diagnosis.
A 22-year-old male with megalencephalic leukoencephalopathy with subcortical cysts. (a) Axial fluid-attenuated inversion-recovery and (b) axial T2weighted images reveal bilateral anterior temporal lobe cysts (white arrows), deep (black arrow) and subcortical (open arrow) white matter hyperintensity. Temporal lobe cysts with extensive white matter lesions involving the deep and subcortical white matter, and external capsule with sparing of basal ganglia, thalami and internal capsules are typical for this subtype of van der Knaap leukoencephalopathy.
A 35-year-old female with cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy. (a) Axial T2weighted image shows confluent hyperintense lesions in both anterior temporal lobes (open arrows). (b) Axial fluid-attenuated inversion-recovery image shows patchy subcortical hyperintense areas (white arrows) and multiple lacunar infarcts (thin white arrow). (c) AxialT2 weighted image shows multiple patchy hyperintense areas involving the external capsule (open arrow), insular cortex (thin arrow) and basal ganglia (asterisk).
A 26-year-old male with paraneoplastic limbic encephalitis presenting with progressive memory disturbance. (a) Initial coronal T2weighted image demonstrates swelling and increase signal in both mesial temporal lobes (white arrows). (b) Follow-up coronal T2weighted image after 1 year shows significant decrease in the swelling and abnormal signal intensity (white arrows). (c) Axial contrast-enhanced CT section through the mid-abdomen shows ileocolic intussusception (black arrow) with marked concentric wall thickening of ascending colon (white arrows). Biopsy proven Burkitt's lymphoma of ascending colon is also shown.
Temporal and frontal lobe seizures differential semiological features.
Features Temporal Frontal
Sz frequancy Less frequent Often daily
Sz onset Slower Abrupt, explosive
Sleep activation Less common Characteristic
Progression Slower Rapid
Automatisms Common-longer Less common
Initial motionless stare Common Less common
Complex postures Late, less frequent, less prominent Frequent, prominent, and early
Hypermotor Rare Common
Bipedal automatisms Rare Characteristic
Somatosensory Sx Rare Common
Vocalization Speech (nondominant)Loud, nonspeech (grunt, scream, moan)
Seizure duration Longer Brief
Secondary generalization Less common Common
Postictal confusion More prominent-longer Less prominent, Short
Postictal aphasia Common in dominant hemisphere Rare unless spreads to temporal lobe
Feature Location
Automatism
Unilateral limb automatism Ipsilateral focus
Oral automatism (m)Temporal lobe
Unilateral eye blinks Ipsilateral to focus
Postictal cough Temporal lobe
Postictal nose wiping Ipsilateral temporal lobe
Ictal spitting or drinking Temporal lobe focus (R)
Gelastic seizures(m)Temporal, hypothalamic, frontal
(cingulate)
Dacrystic seizures (m)Temporal, hypothalamic
Unilateral limb automatisms Ipsilateral focus
Whistling Temporal lobe
Semiological Features (TLE) - Lateralizing or Localizing Value.
Autonomic
Ictal emeticus Temporal lobe focus (R)Ictal urinary urge Temporal lobe focus (R)Piloerection Temporal lobe focus (L)
Speech
Ictal speech arrestTemporal lobe (usually dominant hemisphere)
Ictal speech preservation Temporal lobe (usually nondominant)
Postictal aphasiaTemporal lobe (dominant
hemisphere)
Motor
Early nonforced head turn Ipsilateral focus
Late version Contralateral focus
Eye deviation Contralateral focus
Focal clonic jerking Contralateral perirolandic focus
Asymmetrical clonic ending Ipsilateral focus
Fencing (M2E)Contralateral (supplementary
motor)
Figure 4Contralateral to the extended limb
(temporal)
Tonic limb posturing Contralateral focus
Dystonic limb posturing Contralateral focus
Unilateral ictal paresis Contralateral focus
Postictal Todd’s paresis Contralateral focus
CORRESPONDENCE OF COGNITIVE FUNCTIONSEVALUATED BY MMSE TO SPECIFIC BRAIN AREAS