approach to temporal and limbic system brain lobe anatomy and function

1. Temporal lobe, delineated above (dorsally) by a lateral
sulcus (sylvian fissure)
Occurs only in primates and is largest in man
Approximately 17% of the volume of the human cerebral
cortex, 16% in the right and 17% in the left hemisphere
Temporal cortex includes auditory, olfactory, vestibular,
and visual senses
Perception of spoken and written language.
Addition to cortex, the temporal lobe contains white
matter, part of the lateral ventricle, the tail of the caudate
nucleus, the stria terminalis, the hippocampal formation,
and the amygdala.

4. The medial side with olfaction (the
uncus and nearby cortex)
semantic memory (the hippocampal
formation)
The nearby amygdala generates
responses to perceived sensory stimuli
that have been partly analyzed
elsewhere in the brain. Such responses
include largely involuntary ones,
mediated by the autonomic and somatic
motor systems, and mental functions,
especially those called feelings or
emotions, that motivate decision and
voluntary action

5. 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

9. Hippocampal Formation
The components of the hippocampal formation are the hippocampus, an
enrolled gyrus adjacent to the parahippocampal gyrus
Dentate gyrus, which represents the free edge of the pallium, and the
associated white matter, the alveus, fimbria, and fornix.
The cortex adjacent to the hippocampus is known as the entorhinal area;
it is 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

11. 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
Two named gyri of the anterior end of the uncus, the ambient and
semilunar gyri consist of periamygdaloid cortex that 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

12. White Matter
Subcortical white matter comprises three populations of axons.
Association fibres connect cortical areas within the same cerebral
hemisphere.
The largest bundle is the arcuate fasciculus, whose anterior end is in the
frontal lobe.
Its above the insula and lentiform nucleus, two-way communication
between 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 fasciculus
Another 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.
The fornix and stria terminalis

13. 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 fibres afferent to the temporal cortex include medial geniculate body
to the primary auditory area
which is connected with the amygdala, hypothalamus, hippocampal
formation, and parahippocampal gyrus
Important 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.

14. Temporal Lobe Function
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)

15. Sensory Processes
Identification and Categorization of
Stimuli
Cross-Modal Matching
Process of matching visual and
auditory information
Affective Responses
Emotional response is associated with
a particular stimulus
Spatial Navigation
Hippocampus – Spatial Memory
Temporal Lobe Function

16. Special face
processing pathway
Faces

17. Asymmetry of Temporal Lobe Function
Left temporal lobe
Verbal memory
Speech processing
Right temporal lobe
Nonverbal memory
Musical processing
Facial processing

18. Symptoms of Temporal-Lobe Lesions

19. Clinical Neuropsychological Assessment of Temporal-
Lobe DamageTests do not assess all possible temporal-
lobe symptoms

20. Arterial Blood Supply and Venous Drainage
The 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.

21. The venous drainage of the temporal cortex
Into the superficial middle cerebral vein and also into the inferior
anastomotic vein (vein of Labbé)
superficial middle cerebral vein with the transverse sinus
Blood from interior of the lobe, including the 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.

47. 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.

48. 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.

49. Bilateral temporal lobe hyperintensity Advanced MRI findings
S. no. Diagnosis
Clinical
features
Lobe GM WM Additional MRI findings DWI SWI MRS Gd-enhancement Laboratory result
1 Herpes encephalitis
Fever,
seizure,
altered
sensorium
A, M + −
Orbital gyri
involvement, gyriform
haemorrhages
R + ND Gyriform
HSV antibodies in
CSF
2
Mesial temporal
sclerosis
Complex
partial
seizure
M + +
Hippocampal,
mamillary body, fornix
and collateral WM
atrophy
− − ND ND
Temporal lobe
localisation on
EEG
3 Gliomatosis cerebri
Headache,
recurrent
seizures
A, M + +
Expansion of
parenchyma, multilobar
involvement
− − ↑ML Absent / patchy
Non-
contributory
4 MELAS
Episodes of
LOC, seizure
P, M + +
Fleeting hyperintensity,
basal ganglia
involvement
R − ↑lac Patchy
↑Serum and CSF
lactate
5 Alzheimer's disease
Personality
changes,
memory loss
A, M − +
Hippocampal atrophy,
enlarged
parahippocampal
fissures
− − ↑ML − Non-contributory
6 MLC
Development
al delay,
seizure
Whole − +
Temporal lobe cysts,
subcortical WM,
external capsule
− − ↓NAA ↑cho − Non-contributory
7 Congenital CMV Seizure P − +
Periventricular cysts,
pachygyria-agyria
complex
− − ND − Non-contributory

50. 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.

51. 8 CADASIL
Migraine,
hemisensory
loss
A, M − +
Lacunar infarcts,
subcortical WM,
external capsule and
insula
− − ND −
Non-
contributory
9
Frontotemporal
dementia
Dementia A,M − +
Fronto-temporal
atrophy
− − ↓NAA ↑cho −
Non-
contributory
10 Limbic encephalitis
Memory
disturbance
M + −
Cingulate gyrus,
subfrontal cortex and
inferior frontal WM
− − ND −
Pleocytosis,
lymphoma
antibodies in
CSF
11 Hyperammonemia
Confusion,
altered
sensorium
A + −
Posterior cingulate
gyrus
R − ND ND ↑Blood ammonia
12 Wilson's disease
Weakness,
extrapyrami
dal
symptoms
A, P, L + +
Fronto-parietal lobes,
dorsal midbrain, deep
grey nuclei
R − ND −
↑Serum and
urine copper,
↓ceruloplasmin
13
Myotonic
dystrophy
Development
al delay,
facial and
distal limb
weakness
A − +
Periventricular and
deep WM, prominent
VR spaces
− − ND ND
Myotonic
discharges in
electromyograph
y

52. 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).

53. 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.

54. 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

55. 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).

56. 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.

57. 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)

58. 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.

59. 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.

60. 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.

61. 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.

62. 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.

63. 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.

64. 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).

65. 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.

66. 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

67. 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.

68. Autonomic
Ictal emeticus Temporal lobe focus (R)
Ictal urinary urge Temporal lobe focus (R)
Piloerection Temporal lobe focus (L)
Speech
Ictal speech arrest
Temporal lobe (usually
dominant hemisphere)
Ictal speech preservation
Temporal lobe (usually
nondominant)
Postictal aphasia
Temporal lobe (dominant
hemisphere)

69. 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 4
Contralateral 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