Occipital lobe
The cerebral hemisphere is divided into five lobes, frontal, parietal, occipital, temporal and insula.
It is located in the posterior part of the hemisphere, posterior to the occipitoparietal sulcus.
It is small on the lateral side and the sulcus is variable.
After the parietal and temporal lobes, the part of the brain at the posterior end of the cerebellum above the cerebellum is called the occipital lobe (occipitallobe).
The occipital lobe lies behind the line connecting the occipito-parietal fissure and the anterior occipital notch (Scherer’s sulcus). Medially, between the talar fissure and the parieto-occipital fissure is the cuneate lobe, and between the lateral parietal fissure alternates is the lingual gyrus. It is responsible for processing visual information.
The occipital lobe is responsible for language, motor sensation, abstract concepts and vision.
The conduction pathway of visual information from the retinal photoreceptors to the occipital visual centers of the brain is called the optic pathway.
The occipital lobe is the visual cortical center. In occipital lobe lesions, not only visual impairment occurs, but also symptoms such as memory deficits and motor perception impairment, but mainly visual symptoms.
Occipital lobe symptom cluster
The occipital lobe is the visual cortical center. In occipital lobe lesions, not only visual impairment, but also memory deficits and motor perception impairment occur, but mainly visual symptoms.
Causes
1, craniocerebral trauma: easy to cause occipital contusion, cortical blindness can appear after the injury, limited injury can be seen quadrant blindness.
Cerebrovascular disease: occlusion of the parieto-occipital branch of the middle cerebral artery in the dominant hemisphere, and Gerstmann’s syndrome appears on the opposite side of the lesion.
3.Tumor: Glioblastoma of occipital lobe develops from posterior occipital and posterior temporal cortices to subcortical white matter, and hemianopsia appears when it invades the posterior limb of the internal capsule.
Clinical manifestations
1.Visual hallucination: When the occipital lobe is damaged and the visual center is lesioned, it will cause hallucinations, such as flashing lights and pictures, etc., and can appear simultaneously with visual distortion.
2, visual field defects: small focal damage to one side of the occipital lobe, causing isotropic hemianopia central dark spot. Cerebrovascular lesions on one side of the occipital lobe cause isotropic hemianopia.
3.Visual cognitive impairment: Patients cannot recognize words visually; cannot recognize common objects; cannot recognize space and face; cannot clarify the orientation relationship and distance difference between objects.
4, eye movement disorders: occipital lobe lesions can occur Balint visual paralysis, the patient gaze to the right, there is no rapid shift of vision to the left.
5.Memory impairment: visual representation is absent, the patient can reason normally and retell distant experiences, but near memories cannot, or even fictitious.
6.Motion perception disorder: when patients see moving objects, they only see the arrangement of the order of objects, they do not fully experience the speed of object movement, they do not estimate the time of movement experience, and they cannot see the movement of objects.
Differential diagnosis
1. Occipital lobetumor (occipitallobetumor) Occipital lobetumor often involves the posterior part of parietal and temporal lobes. In the early stage, there is only a defect of the lesion on the visual field, amblyopia or loss of color vision. The main findings are contralateral isotropic or quadrantal blindness and simple immature visual hallucinations and distortion of visual objects in the contralateral visual field. The disease often presents with visual episodes, and the site of hallucinations is relatively constant, mostly within the contralateral visual field of the lesion. The frequency of episodes gradually increases, and as the number of episodes increases, localization symptoms such as hemianopia, aphasia, and loss of recognition appear one after another. Visual episodes are not related to the environment.
2. Internal carotid artery occlusion (arteriacarotisintermaoblilation) presents with hemianopia of the contralateral visual field and paralysis of the upper and lower extremities and hemianesthesia, i.e., the triple hemianopia sign. Sometimes the hemianopia manifests as quadrant blindness, especially in the lower 1/4. The disease is characterized by crossed ocular-cone bundle paralysis, transient black clouding on the side of the lesion, optic nerve atrophy in the fundus, and hemiplegia on the opposite side.
3.occlusion of posterior cerebral artery (oscclusionofposteriorcerebralartery) can have hemianopia, which can be complete or incomplete, and the latter is mostly upper 1/4 quadrant blindness. It may be accompanied by named aphasia and dyslexia. Occlusion of the posterior cerebral artery on both sides may present as bilateral isotropic hemianopia and macular aversion. There is often transient blackness and fogginess in front of both eyes. After a long period of time, pallor is seen in the papillae of the hemianopsia side.
4.Schilder’s disease (Schilder’sdisease) often develops in children. Ocular symptoms include decreased visual acuity, isotropic hemianopia, or cortical blindness. There are usually no fundus changes. When the lesion involves the optic tract and optic cross, pallor of the optic head and blunted light response may occur. In addition, the disease often has symptoms of intellectual impairment, damage to the motor system and sensory system.
5, multiple sclerosis (multiplesclerosis) more than half of the patients with this disease appear retrobulbar optic neuritis. Acute ophthalmoplegia, accompanied by rapid vision loss, one to two days can appear blind, can be first for one side, and then involved in the other side. The pupil is dilated, the light reflex is diminished, the central dark spot can be 10° to 20°, and there is often no change in the peripheral visual field. Recovery from the above symptoms is generally rapid, but recurrence is often observed.