Practical Radiology

Neuropsychiatry block 222 7/2/2019 Neuropsychiatry block 222

The brain can be divided into left and right cerebral hemispheres. Each cerebral hemisphere is divided into six sections, called "lobes": frontal lobe, parietal lobe, temporal and occipital lobe; plus two other that are not visible from outside: Insula and limbic lobe. To locate these different lobes of the brain, a 3D reconstruction was made​ from a MRI exam of the head. The skull was removed using scissors provided by software (image subtraction processing).

Frontal Lobe The frontal lobe is located in the anterior part of the cerebral hemispheres: • Anterior to the parietal lobe. (The frontal lobe is separated from the parietal lobe by the central sulcus (of Rolando)).

Temporal Lobe The temporal lobe is located in the lower part of the cerebral hemispheres: • Inferior to the frontal lobe and parietal lobe. The temporal lobe is separated from the frontal lobe by the lateral sulcus (or Sylvian fissure). • Anterior to the occipital lobe. The temporal lobe is virtually continuous with the occipital lobe.

Parietal Lobe The parietal lobe is located in the upper part of the cerebral hemispheres: • posterior to the frontal lobe • superior to the temporal lobe • the parietal lobe is partially separated from the temporal lobe by the Sylvian fissure (lateral sulcus). • Anterior to the occipital lobe. • The parietal lobe is separated from the occipital lobe by the parieto- occipital sulcus to the middle part

Occipital Lobe The occipital lobe is located in the posterior part of the cerebral hemispheres: • posterior to the temporal lobe and parietal lobe • the occipital lobe is partially separated from the parietal lobe by the parietooccipital fissure. • In addition, there is only virtual separation between the temporal lobe and occipital lobe.

Insular lobe (Insula) The Insular lobe (nsula) is located in depth of Sylvian fissure. The cortex of the insula is covered by frontal operculum, parietal operculum and temporal operculum. The insula has five gyri.

Basal Ganglia (overview) • Lentiforme Nucleus = putamen + globus pallidus • Corpus striatum = caudate nucleus + putamen + globus pallidus • Neostriatum = caudate nucleus + putamen. Basal ganglia denote the nuclei of gray matter deep below the cerebral hemispheres.

The Circle of Willis The Circle of Willis is an arterial polygon formed as the ICA and vertebral systems anastomose around the optic chiasma and infundibulum of the pituitary stalk. This communicating pathway allows equalization of blood-flow between the two sides of the brain, and permits anastomotic circulation, should a part of the circulation be occluded. 7/2/2019 اسم ورقم المقرر – Course Name and No.

anterior circulation: left and right internal carotid arteries (ICA) horizontal (A1) segments of the left and right anterior cerebral arteries (ACA) single anterior communicating artery (ACOM) posterior circulation: left and right posterior communicating arteries (PCOM) (although some consider the PCOM to be anterior circulation) horizontal (P1) segments of left and right posterior cerebral arteries (PCA) single basilar artery (tip) 7/2/2019 اسم ورقم المقرر – Course Name and No.

Regional Blood Supply to the Cerebrum There are three cerebral arteries; anterior, middle and posterior. They each supply a different portion of the cerebrum. The anterior cerebral arteries supply the anteromedial portion of the cerebrum. The middle cerebral arteries are situated laterally, supplying the majority of the lateral part of the brain. The posterior cerebral arteries supply both the medial and lateral parts of the posterior cerebrum.

MRA of Circle of Willis. AP view with rotations.  1, Internal carotid artery.  2, Posterior cerebral artery.  3, Anterior cerebral artery (A1).  4, Anterior cerebral artery (A2).  5, Middle cerebral artery.  6, Basilar artery.  7, Vertebral artery.

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