| disease | Parietal Lobe Tumor |
The incidence of parietal lobe tumors is lower than that of frontal and temporal lobe tumors. The majority of these tumors are gliomas, accounting for approximately 8.52% of intracranial gliomas; followed by meningiomas, making up about 6.50% of intracranial meningiomas; and then metastatic tumors. They predominantly occur in adults. The parietal lobe has highly complex functions, primarily involving the analysis and integration of various sensory information to distinguish and determine the nature and location of stimuli. Therefore, damage caused by parietal lobe tumors mainly manifests as sensory disturbances in the contralateral half of the body. Most patients exhibit definitive symptoms and signs, particularly when accompanied by focal sensory seizures, which hold greater diagnostic value for localization. Over decades of research on parietal lobe disorders such as constructional apraxia, hemianesthesia, disorientation, and Gerstmann syndrome, our understanding of parietal lobe symptoms has significantly improved. Based on the symptoms and signs presented by patients, relatively accurate localization diagnoses can be made. However, there are indeed a few cases, especially those involving slow-growing meningiomas, where even extensive involvement of the parietal lobe may not produce obvious symptoms.
bubble_chart Clinical Manifestations
Damage caused by parietal lobe tumors primarily manifests as sensory disturbances on the contralateral side of the lesion, affecting functions such as vision and language.
1. Sensory disturbances Sensory disturbances are divided into general sensory disturbances and cortical sensory disturbances. General pain and temperature disturbances caused by parietal lobe tumors are often not obvious, and even if they occur, they are usually limited to the distal extremities, presenting as very mild glove- or stocking-type sensory disturbances. This is due to the thalamus also receiving some pain and temperature impulses. Cortical sensory disturbances mainly manifest as impaired position sense, two-point discrimination, tactile localization, and graphognosia in the contralateral limbs. For example, when a patient closes their eyes and holds an object, they may feel it but cannot judge its weight, size, shape, or texture. They may even fail to recognize simple numbers written on their skin. Consequently, they cannot perform a comprehensive analysis of the object, a condition known as astereognosis. This results from extensive damage to the superior parietal lobule of the postcentral gyrus. Cortical sensory disturbances can also manifest as sensory neglect, where stimulation of the affected limb may feel completely normal or slightly diminished. However, when both limbs are stimulated simultaneously, only the unaffected limb is perceived, while the affected limb is entirely ignored. After the tactile stimulus on the affected limb is removed, the patient may still feel the sensation persist for some time, a phenomenon known as tactile persistence.
2. Body schema disorders Patients experience difficulty recognizing their own body structure, a phenomenon more common in right parietal lobe lesions. The underlying mechanism remains poorly understood. Clinical manifestations vary widely. For instance, some patients show indifference to their hemiplegia, as if it were unrelated to them, displaying no anxiety—a condition called anosodiaphoria. Others completely deny their hemiplegia, even when shown the paralyzed limb, insisting it is not theirs or attributing it to someone else’s hand or foot. They may also offer unrelated explanations for their inability to move the limb, a phenomenon known as anosognosia. Some patients experience a loss of limb sensation, believing the paralyzed limb no longer exists or belongs to them, as if their own limb has been lost. Another manifestation is the sensation of having an extra limb or limbs, termed phantom polyposia. Other symptoms include finger agnosia, left-right disorientation, and autotopagnosia.3. Constructional apraxia Constructional apraxia refers to the inability to correctly perceive, distinguish, or assemble spatial relationships involving objects, buildings, drawings, or patterns. Patients struggle to understand these relationships or use tools properly, leading to difficulties in daily life. Clinically, this can be assessed through drawing or block-building tasks. Although patients can imitate, the overall layout and proportions are often distorted, with elements misplaced, overcrowded, or scattered, losing the original shape and spatial concept. The mechanism underlying constructional apraxia remains controversial.
4. Gerstmann syndrome This syndrome occurs with lesions in the angular gyrus, supramarginal gyrus, or the transitional area between the parietal and occipital lobes. Its clinical manifestations primarily include finger agnosia, left-right disorientation, agraphia, and acalculia. Finger agnosia is the most common symptom, often bilateral. When asked to identify specific fingers, patients cannot recognize them and exhibit confusion, particularly with the thumb, little finger, and middle finger. Finger agnosia is a key component of Gerstmann syndrome. Left-right disorientation affects not only the patient’s own body but also their ability to distinguish left and right in others, though environmental orientation may remain intact. Agraphia mainly manifests as difficulty writing, though reading or copying may be unaffected. Acalculia is particularly evident in written calculations.
(1) Subcortical alexia: The patient is unable to comprehend written or printed words and cannot pronounce them, but spontaneous writing and copying remain unimpaired. The patient can express thoughts through writing but cannot read their own written articles or letters. Subcortical alexia is often accompanied by hemianopia.
(2) Cortical alexia: In addition to being unable to recognize or comprehend written words, the patient often exhibits agraphia, being incapable of dictation, copying, or spontaneous writing.
6. Epileptic Seizures Epileptic seizures caused by parietal lobe tumors are mostly focal and often sensory in nature, manifesting as paroxysmal sensory abnormalities on the side contralateral to the lesion. The initial site commonly involves the thumb and index finger, though onset in the foot is not rare. Symptoms primarily include paroxysmal numbness, electric shock-like sensations, or pain, spreading in a fixed direction. However, motor symptoms such as focal muscle spasms or clonus may also occur, or sensory symptoms may precede motor symptoms, even progressing to generalized seizures. Postictal transient sensory disturbances, such as impaired two-point discrimination, stereognosis, and position sense, are common.
7. Hemiplegia or Monoplegia Parietal lobe tumors often cause hemiplegia or monoplegia in the limbs contralateral to the lesion. Paralysis is not a symptom of the parietal lobe itself but results from tumor invasion into the motor area. Concurrent with paralysis, hyperactive deep reflexes may be observed, though increased muscle tone is usually not prominent.
bubble_chart Auxiliary Examination
1. Skull Plain Film Tumors in the parietal lobe, like tumors in other parts of the cerebral hemisphere, can cause varying degrees of skull changes depending on the nature of the tumor. For example, meningiomas may lead to localized hyperostosis or destruction of the inner table of the skull.
2. Ultrasound In ultrasound examinations of parietal lobe tumors, midline shift to the contralateral side is commonly observed.
3. Electroencephalogram (EEG) The EEG characteristics of parietal lobe tumors include: widespread localized δ or θ waves, primarily over the affected parietal region, spreading to the occipital, posterior temporal, anterior temporal, posterior frontal, and inferior parietal areas. Particularly in cases of parasagittal tumors near the falx cerebri, the range of slow waves is even broader, often making it difficult to distinguish from temporo-occipital tumors. When δ waves are confined to the parietal or parieto-occipital regions, the likelihood of a parietal lobe tumor is higher. For deep parietal lobe tumors, localized δ waves are generally less pronounced, often displaying 5–7 Hz localized scattered or continuous θ waves and lazy waves. Parietal lobe tumors frequently induce widespread scattered slow waves in the affected hemisphere (about 30%) or both hemispheres (about 10%), sometimes showing generalized spike-and-slow waves, with disrupted background α waves in the affected or both hemispheres.
4. Cerebral Angiography The angiographic features of parietal lobe tumors include: - In anteroposterior (AP) views, the anterior cerebral artery shows parallel lateral displacement, while the convexity branches of the middle cerebral artery are displaced downward or partially separated. - In lateral views, the main trunk of the middle cerebral artery is depressed, and vessels in the tumor area are compressed.
(1) Parasagittal Tumors Near the Falx Cerebri: - AP view: The anterior cerebral artery shifts contralaterally in a straight line, with significant distal displacement. - Lateral view: If the tumor is anterior, the pericallosal artery and its branches appear arched; if posterior, the distal pericallosal artery is pressed anteroinferiorly or pushed forward, with straightened or arched terminal branches. The middle cerebral artery group is slightly displaced forward and downward, or its branches are dispersed.
(2) Parafalcine Tumors Near the Superior Sagittal Sinus: - AP view: The anterior cerebral artery shifts contralaterally, with marked displacement at the upper end. The pericallosal artery branches are depressed into an arch, and the falx sign is positive. The middle cerebral artery group is uniformly compressed and lowered. - Lateral view: The middle cerebral artery group is displaced downward, and the pericallosal artery is slightly depressed or straightened. Since these are often meningiomas, the anterior and middle cerebral arteries may appear tortuous and thickened.
(3) Fronto-Parietal Tumors: - AP view: The anterior cerebral artery shows an arcuate contralateral shift. The middle cerebral artery group is displaced downward (Grade I). The vascular changes lack an "O"-shaped pattern. - Lateral view: The main trunk of the middle cerebral artery is notably flattened. The frontoparietal ascending branches show more pronounced changes than in tumors elsewhere, appearing compressed, straightened, or separated.
5. Ventriculography Since the posterior body and trigone of the lateral ventricle correspond to the parietal lobe, parietal lobe tumors often depress the lateral ventricular body, with the septum pellucidum and third ventricle obliquely displaced contralaterally. Tumors closer to the occipital region (parieto-occipital tumors) may displace the trigone and occipital horn downward.
6. Brain CT Scan CT offers more advantages than other auxiliary diagnostic techniques for detecting intracranial tumors, especially supratentorial tumors, making it the preferred diagnostic method currently. {|108|}
(1) Chronic subdural hematoma Chronic subdural hematoma in the parietal lobe is a common clinical condition, predominantly seen in middle-aged and young adults. Its clinical course resembles that of a brain tumor, but all cases have a history of head trauma, often minor and easily forgotten by patients, who may not voluntarily mention it or even recall it when questioned. Clinical symptoms gradually appear after months or even years. Early symptoms often include headache and dizziness, and localized sensory epilepsy or hemisensory disturbances may also be detected. Careful examination can reveal signs and symptoms of parietal lobe damage. Skull X-rays may show manifestations of chronic intracranial hypertension, usually without fracture lines. Ultrasound examination may reveal midline shift (though bilateral cases may show no shift). Electroencephalography (EEG) may show localized slow waves. Carotid angiography often demonstrates an avascular area, confirming the diagnosis.
(2) Brain abscess The incidence of parietal lobe brain abscess is lower than that of temporal or frontal lobe abscesses. Most cases result from hematogenous infections. The acute phase often presents with systemic symptoms (high fever, polymorphonuclear leukocytosis in peripheral blood) and acute intracranial hypertension. Lumbar puncture reveals purulent changes in cerebrospinal fluid, making it easy to differentiate from a brain tumor. However, chronic parietal lobe abscesses have a prolonged course, and their clinical symptoms resemble those of parietal lobe tumors, often making differentiation difficult. A definitive diagnosis can only be made during surgical exploration.
(3) Cerebrovascular disorders In cases of middle cerebral artery disorders, such as vascular malformations, arteriovenous fistulas, aneurysms, or arteriosclerosis, parietal lobe syndrome may occur. The junction of the parietal, temporal, and occipital lobes supplied by the middle cerebral artery is prone to ischemic softening. When the angular gyrus of the dominant hemisphere is affected, agraphia, alexia, and Gerstmann syndrome may manifest. Careful examination is necessary to differentiate these conditions from tumors.
