bubble_chart Overview

Frontal lobe tumors are common intracranial tumors, accounting for the highest incidence among supratentorial tumors, representing approximately one-fifth of all intracranial tumors. Gliomas are the most frequent, constituting about 25.57% of all intracranial gliomas, followed by meningiomas, which make up roughly 11.45% of all intracranial meningiomas. Additionally, congenital tumors and metastatic tumors often occur in this region. Frontal lobe tumors are more common in adults, with no significant gender difference. Although these tumors are prevalent, the understanding of the frontal lobe's anatomical structure and neurophysiological functions remains incomplete. Over the past two decades, advancements in neurosurgery, neurophysiology, and neuropsychiatry have led to a deeper understanding of the neurophysiological functions of the frontal lobe and the symptoms caused by its lesions. However, a comprehensive and thorough understanding is still lacking, particularly regarding the right frontal lobe, which is often referred to as the "silent area" or "non-dominant area." Patients with such tumors often exhibit no obvious clinical symptoms or signs in the early stages and rarely show significant functional impairments, making early diagnosis challenging and impacting treatment outcomes and prognosis.

bubble_chart Clinical Manifestations

Frontal lobe tumors generally grow slowly and have a long medical history, with early symptoms being inconspicuous. During the course of the disease, apart from symptoms of increased intracranial pressure such as headache, vomiting, and optic disc edema, the main clinical symptoms are related to mental, emotional, motor, speech, and cerebellar coordination functions.

1. **Mental Symptoms** Mental symptoms can occur with tumors in other parts of the brain, but those caused by frontal lobe tumors are more prominent, appear earlier, and have a higher incidence, especially when both frontal lobes are affected. The mental symptoms of frontal lobe tumors mainly manifest as memory impairment and personality changes, which are more common in tumors located in the anterior or basal frontal lobes. Early symptoms often include difficulty concentrating, reduced memory and comprehension, particularly noticeable in short-term memory loss while long-term memory is preserved. As the disease progresses, thinking and integrative abilities significantly decline, both recent and remote memory gradually deteriorate, and patients lose insight and judgment, developing disorientation to time and place, eventually leading to dementia. Personality changes are also common, primarily characterized by intellectual impairment, apathy, indifference to surroundings, neglect of personal hygiene, and laziness. Some patients exhibit loss of inhibitory control, becoming easily agitated, irritable, euphoric, or displaying childish humor, frivolity, foolishness, or annoying jokes, and may even experience forced crying or laughing. In some cases, patients may show extreme enthusiasm or outbursts of rage, accompanied by piloerection, elevated blood pressure, dilated pupils, and aggressive behavior.

The mental symptoms caused by frontal lobe tumors usually develop slowly. Obvious mental symptoms are easier to detect, but in the early stages, subtle mental changes often go unnoticed and are only discovered upon detailed questioning of the patient’s relatives. The incidence of mental symptoms in frontal lobe tumors is generally around 60%. Mental symptoms can occur at some stage in the progression of tumors in any intracranial location. Besides lesions in various lobes of the cerebral hemispheres, infratentorial lesions and increased intracranial pressure can also cause mental symptoms. Therefore, relying solely on mental symptoms is insufficient for diagnosing frontal lobe tumors.

2. **Epileptic Seizures** In frontal lobe tumors, epileptic seizures are often the first symptom, with an incidence of about 33.3%. Among these, 4/5 are generalized seizures without aura, and 1/5 are focal seizures. When the tumor invades cortical areas 6 and 8 in the anterior frontal lobe, seizures often involve loss of consciousness, with the head and eyes turning to the side opposite the lesion and convulsions in the contralateral limbs (more pronounced in the upper limbs). In a few patients, the seizure stops at this stage, but most progress to generalized tonic-clonic seizures. Tumors in the basal frontal region, especially near the midline, may cause generalized convulsions due to increased intracranial pressure as the tumor spreads bilaterally. Invasion of the precentral gyrus can also lead to focal seizures, with convulsions in corresponding contralateral body parts depending on the affected area. For example, if convulsions start in the thumb or index finger, the lesion is likely in the lower part of the precentral gyrus; if they begin at the corner of the mouth, the lesion is at the very bottom of the precentral gyrus, near the lateral fissure. Convulsions starting in the foot or toes are extremely rare, and if they occur, the lesion should be considered in the medial parasagittal region. Observing the progression of focal seizures is highly valuable for tumor localization. Additionally, if focal seizures progress to generalized seizures, it often indicates organic disease. If the patient had paralysis before the seizure, the seizure may temporarily worsen it. Temporary paralysis appearing after a seizure in a previously unaffected patient is called Todd’s paralysis, which is not uncommon clinically. In some cases, patients may exhibit repetitive movements of certain muscle groups, such as continuous blinking or body twisting.

3. Pyramidal tract damage symptoms  Frontal lobe tumor seasonal disease The weakening or disappearance of the contralateral abdominal wall and cremasteric reflexes, along with the simultaneous appearance of rigid metatarsus flexion reflex, is often an early symptom. As the tumor continues to grow and the degree of invasion into the motor area increases, increased muscle tone and hyperactive tendon reflexes may appear on the contralateral side of the lesion, often accompanied by ankle clonus, patellar clonus, and wrist clonus. Eventually, varying degrees of paralysis may occur on the contralateral side of the lesion. The Babinski sign is a representative and important sign of corticospinal tract pathology, which can appear with tumors in any part of the frontal lobe motor cortex. Anatomically, due to the oblique forward projection of the facial motor cortex area, it is highly susceptible to damage. Therefore, frontal lobe tumors often present with contralateral central deviation of the mouth, with an incidence rate of 44.8%. This sign is particularly noticeable during laughter or conversation and is thus considered one of the important signs of frontal lobe tumors. Additionally, because frontal lobe tumors can easily compress or invade the contralateral hemisphere through the falx cerebri, bilateral pyramidal tract signs or ipsilateral pyramidal tract signs may occur.

4. Motor Aphasia In patients with right hemisphere dominance, when a tumor invades the posterior part of the left inferior frontal gyrus (Broca's area), it can lead to motor aphasia. The clinical features are as follows: the patient's lips and tongue can move freely, they can understand others' speech, but cannot engage in verbal dialogue with others. There is no impairment in the movement of the articulatory organs; some may produce sounds but cannot form coherent language. Patients with milder damage often exhibit incomplete motor aphasia, where they can produce individual sounds but cannot form words from these sounds or arrange them in the necessary order. Their speech is slow, often mispronouncing words or experiencing pauses and stuttering, making the individual sounds they produce chaotic and incomprehensible. In severe cases, the ability to speak is completely lost.

When a tumor affects the posterior part of the middle frontal gyrus in the dominant hemisphere, it can lead to agraphia. The patient can speak, understand, and read but loses the ability to write. Clinically, it is common to encounter patients with complete motor aphasia who not only lose the ability to speak but also exhibit agraphia.

5. Frontal Ataxia Aphasia The ataxia caused by frontal lobe tumors is due to damage to the fronto-ponto-cerebellar tract. Anatomically, frontal lobe fibers reach the pons, then cross via transverse pontine fibers to the contralateral middle cerebellar peduncle, extending to the cerebellar dentate nucleus. From there, most fibers terminate in the red nucleus, while a minority project from the red nucleus to the ventral lateral thalamic nucleus and then to the motor area. This constitutes the so-called cortico-cerebello-cortical circuit. Therefore, frontal lobe tumors can produce ataxia similar to that of cerebellar origin. In the early stages of a frontal lobe tumor, especially in the frontal pole, if not accompanied by increased intracranial pressure, there is no motor impairment or paralysis. However, complex, delicate, and higher-order motor impairments may occur, such as clumsiness and incoordination during activities like embroidery, threading a needle, or performing repetitive actions. There may also be contradictions between speech and action. For example, when asked to pick up an object, the patient may clearly verbalize the action but exhibit antagonistic, clumsy, or incorrect movements, demonstrating a disconnect between speech and action. Tremors may appear in the contralateral hand, and mild ataxia may be present in the lower limb, though these are not easily observed under normal circumstances. They may become apparent when the patient is asked to walk quickly or make rapid turns. Some believe that about half of patients with frontal lobe damage may develop ataxia. When both frontal lobes are significantly affected, the patient's gait becomes unsteady and staggering. When one side is predominantly affected, the contralateral lower limb exhibits significant clumsiness, often stepping excessively outward while walking. However, such patients typically do not show prominent dysmetria or impaired sequential motor function, and most do not exhibit ocular tremors.

6. Grasp Reflex and Groping Movements When a frontal lobe tumor damages the posterior part of the frontal lobe, especially the superior frontal gyrus near the precentral gyrus, the ability to control voluntary movements is lost. When an object touches the palm or fingers of the contralateral hand, it triggers flexion of the fingers and palm, causing the patient to grasp the object tightly and not let go—this is called the grasp reflex. When the patient's palm is touched by an object, the hand and arm move toward it. If the palm is continuously stimulated, the arm may explore in various directions until it touches and grasps the object—this is called groping movements. The simultaneous occurrence of grasp reflex and groping movements on one side is often an important diagnostic indicator of a frontal lobe tumor.

7. Other Symptoms   When a frontal lobe tumor is located at or near the base of the frontal lobe, it may affect or compress the olfactory nerve, leading to loss of smell. If the tumor compresses one optic nerve posteriorly, primary atrophy of the affected optic nerve may occur, while the contralateral nerve may exhibit optic disc edema due to increased intracranial pressure (Foster-Kennedy syndrome). Tumors in the medial frontal lobe may sometimes cause urinary incontinence or an urgent need to urinate, leading to frantic urination regardless of location, and even fecal incontinence. Bilateral frontal lobe tumors or tumors invading the precentral gyrus may occasionally result in sucking or smacking reflexes. Deep-seated frontal lobe tumors may rarely present with extrapyramidal symptoms, such as mild tremor in the contralateral limbs. Additionally, frontal lobe tumors may occasionally cause a catatonic state, where patients can maintain a fixed posture for extended periods without fatigue. A few patients may exhibit hyperphagia or hyperfunction of sexual activity.

8. Clinical Features of Tumors in Different Parts of the Frontal Lobe

(1) Tumors in the Anterior Frontal Lobe  Headache or psychiatric symptoms are often the initial symptoms, with pronounced signs of increased intracranial pressure and psychiatric symptoms, while limb motor impairments are rare. Epileptic seizures are typically generalized tonic-clonic without aura. When the tumor invades both frontal lobes, cognitive and psychiatric disturbances become particularly severe. Patients may exhibit only increased intracranial pressure without localized neurological signs.

(2) Tumors in the Middle Frontal Lobe  Clinical manifestations are intermediate between those of the anterior and posterior frontal lobes. Increased intracranial pressure is more pronounced, and psychiatric symptoms are common. Epileptic seizures may present as either generalized or focal. Motor impairments and pyramidal tract signs are more frequent than in anterior frontal tumors but less common than in posterior frontal tumors.

(3) Tumors in the Posterior Frontal Lobe  The initial symptoms are often focal epilepsy or limb weakness. Limb motor impairments and pyramidal tract signs are prominent. Symptoms of increased intracranial pressure are milder compared to anterior and middle frontal tumors, and psychiatric symptoms are less common. Tumors in the left posterior frontal lobe are often accompanied by motor aphasia.

(4) Tumors in the Basal Frontal Lobe  Gliomas are rare here, with meningiomas being more common. In addition to frequent symptoms of increased intracranial pressure, patients often exhibit localized signs such as olfactory disturbances, visual impairments, visual field defects, ipsilateral optic atrophy, and contralateral papilledema, known as Foster-Kennedy syndrome.

bubble_chart Auxiliary Examination

1. Skull Plain Film Skull plain film examination can provide localization or qualitative diagnosis for certain frontal lobe tumors. For example, oligodendrogliomas may exhibit calcifications, often presenting as band-like, speckled, or clustered calcifications that intersect with each other. Astrocytomas typically show calcifications in the cystic wall or tumor mass, appearing as arc-shaped, linear, patchy, or speckled calcifications. Ependymomas frequently occur in the lateral ventricles, commonly displaying speckled calcifications. Meningiomas often exhibit larger, denser, and well-defined calcified masses, with psammomatous meningiomas being the most common. When frontal lobe gliomas, meningiomas, or metastatic tumors are close to the skull, they may cause skull absorption, thinning, destruction, or defects. Additionally, meningiomas often present with skull hyperplasia. In cases of increased intracranial pressure due to frontal lobe tumors, signs such as increased convolutional markings, widened cranial sutures, and changes or displacement of the sella turcica may be observed.

The main characteristics are as follows:

(1) Frontal lobe base tumors

1) Anteroposterior view: The lateral ventricle may shift slightly to the healthy side, with unclear demarcation of the affected ventricle and elevation of the anterior horn floor.

2) Lateral view: The anterior horn may shift posteriorly or superiorly, appearing narrowed with a flattened floor and arc-shaped or mass-like indentations. The front of the lateral ventricle may flatten or show arc-shaped compression. The third ventricle fills well, with flattening and posterior displacement of its lower part. The cerebral aqueduct and fourth ventricle remain normal.

(2) Frontal pole tumors

1) Anteroposterior view: The affected ventricle appears indistinct due to occlusion or narrowing of the anterior horn caused by the tumor. The lateral ventricle shifts to the healthy side, and the septum pellucidum and third ventricle move linearly to the opposite side. If the tumor involves both sides, displacement may be minimal or absent.

2) Lateral view: The anterior horn is occluded, with arc-shaped compression or filling defects at the front of the lateral ventricle, shifting posteriorly. The compression is more pronounced superiorly and less so inferiorly. The anterior horn shortens, narrows, and shifts backward. The anteroinferior third ventricle flattens and shifts posteriorly. The cerebral aqueduct and fourth ventricle remain normal.

(3) Parasagittal frontal lobe tumors

1) Anteroposterior view: The roof of the ipsilateral lateral ventricle is significantly depressed and flattened, with a blunted and displaced superolateral angle. The septum pellucidum and third ventricle often tilt diagonally toward the opposite side. The ipsilateral callosal sulcus and cingulate sulcus also flatten, depress, and shift contralaterally.

2) Lateral view: The anterior horn and anterior body of the lateral ventricle shift downward, with the roof flattened and showing arc-shaped or mass-like indentations. The ventricle may narrow or occlude. The anteroinferior third ventricle flattens and shifts posteroinferiorly. The cerebral aqueduct and fourth ventricle remain unchanged.

(4) Inferior frontal lobe tumors

1) Anteroposterior view: The ipsilateral lateral ventricle shrinks and shifts significantly to the opposite side. The septum pellucidum and third ventricle often curve toward the opposite side.

2) Lateral view: The anterior horn and anterior body of the lateral ventricle shift downward uniformly. The floor of the anterior horn and the tip of the inferior horn may flatten. If the tumor grows posteriorly, the inferior horn narrows and shifts posteriorly. The anteroinferior third ventricle may flatten and shift posteriorly. The cerebral aqueduct and fourth ventricle remain unchanged.

3. Internal Carotid Angiography Frontal lobe tumors primarily affect the supraclinoid segment of the internal carotid artery, the anterior two-thirds of the anterior cerebral artery, and the initial segment of the middle cerebral artery, causing varying degrees and directions of vascular displacement and deformation in the ascending frontal and parietal branches.

The main manifestations are as follows:

(1) Frontal lobe base tumors

1) Anteroposterior view: The horizontal and proximal ascending segments of the anterior cerebral artery shift markedly upward and outward, forming a concave arc that may indicate the tumor's upper boundary. The lower part of the vertical segment of the anterior cerebral artery shifts upward and outward, appearing relatively elevated and shortened. Tumors偏向一侧者，向对侧移位较明显；位于中线或累及两侧者，可无中线移位或移位较轻微。

2) Lateral view: The supraclinoid segment of the internal carotid artery is displaced downward and backward, compressing and flattening the carotid siphon. The branches of the internal carotid artery are displaced posteriorly. If the tumor is close to the midline, the vertical segment and genu of the anterior cerebral artery become straightened and are displaced upward and backward. Extracerebral tumors often appear as an arc, allowing the tumor contour to be outlined. If the tumor is located laterally, the anterior cerebral artery does not show the aforementioned changes, but the middle cerebral artery's sylvian segment may be displaced downward, and the frontoparietal ascending branches become straightened and displaced posteriorly. If the tumor is midline or involves both sides, it may affect both internal carotid arteries and the anterior cerebral arteries.

3) Venous phase: The thalamostriate vein and septal vein appear straightened and displaced upward and backward. The anterior segment of the internal cerebral vein is displaced upward and backward with increased curvature, and the venous angle is also shifted upward. These changes are related to the size of the tumor.

(2) Frontal pole tumor

1) Anteroposterior view: The horizontal segments of the anterior and middle cerebral arteries are straightened, elongated, and grade I downward displacement. The vertical segment of the anterior cerebral artery shows an arcuate shift to the contralateral side, with an increased distance from the middle cerebral artery. The sylvian segment is slightly displaced outward. These vascular changes form a ring-like structure with an open upper edge. The frontal polar artery is often straightened.

2) Lateral view: The vertical and knee segments of the anterior cerebral artery are displaced backward with blunted curvature; the larger and more posterior the tumor, the more pronounced these changes. The frontoparietal ascending artery is straightened and displaced to be decocted later. The closer the tumor is to the midline, the less and milder the downward displacement of the anterior part of the sylvian segment of the middle cerebral artery.

The thalamostriate vein and septal vein may be displaced downward, and the venous angle becomes sharper and shifts backward. The internal cerebral vein shortens and shifts backward with increased curvature, presenting a hump-like appearance.

(3) Parasagittal and parafalcine frontal lobe tumors

1) Anteroposterior view: The anterior cerebral artery is displaced to the contralateral side, more prominently in the upper segment. The pericallosal artery is displaced downward. Parasagittal tumors often show a positive falx sign, while parafalcine tumors show a negative falx sign. The ascending branches of the pericallosal artery shift to the contralateral side and are straightened or arcuately displaced outward and downward on the ipsilateral side. Tumors originating from the free edge of the falx may cause the ipsilateral pericallosal artery and the ascending segment of the anterior cerebral artery to shift outward and downward on the same side, or the bilateral pericallosal arteries and ascending segments of the anterior cerebral arteries to separate and descend.

2) Lateral view: The anterior segments of the pericallosal and callosomarginal arteries are displaced downward with straightened courses, while the curvature of the genu of the corpus callosum becomes sharper. In anteriorly located tumors, the knee of the ascending segment of the anterior cerebral artery is compressed and displaced downward. The callosomarginal artery and its branches are compressed and displaced downward or backward, with the branches appearing arcuate or straightened. In posteriorly located tumors, the proximal and middle segments of the pericallosal artery are displaced downward, and the callosomarginal artery and branches of the pericallosal artery shift forward or backward, often forming an arcuate encirclement around the tumor. The supraclinoid segment of the internal carotid artery, the upper limb of the carotid siphon, the horizontal and sylvian segments of the middle cerebral artery, and the frontoparietal ascending artery may shift to be decocted later or downward with grade I displacement. The venous angle becomes smaller, and the internal cerebral vein shifts to be decocted later or downward.

(4) Mid and posterior frontal lobe tumors

1) Anteroposterior view: The anterior cerebral artery mostly shows a grade I arcuate or square-shaped shift to the contralateral side. The frontal pole sign may be positive. The supraclinoid segment of the internal carotid artery and the horizontal segment of the anterior cerebral artery are displaced downward. The horizontal segment of the middle cerebral artery is stretched and also displaced downward. The sylvian segment may shift downward and outward. When the tumor invades the basal ganglia, the lenticulostriate arteries are straightened and displaced medially.

2) Lateral view: The supraclinoid segment of the internal carotid artery is displaced downward, and the carotid siphon is flattened. The horizontal segment of the middle cerebral artery is displaced downward. The sylvian segment is markedly shifted to be decocted later or downward. In mid-frontal tumors, the anterior group of the frontoparietal ascending branches (i.e., the orbitofrontal and precentral branches) are significantly displaced downward or downward and backward, while the posterior group (i.e., the central and anterior parietal branches) may be straightened. In posterior frontal tumors, the anterior and posterior groups of branches shift forward and downward or to be decocted later, respectively. The sylvian triangle is flattened and displaced downward. When the tumor involves the basal ganglia, the branches of the lenticulostriate arteries become rigid. The internal cerebral vein shifts to the contralateral side, with its anterior segment and venous angle possibly displaced upward and backward. The basal vein shifts downward and inward.

4. Ultrasound In frontal lobe tumors, ultrasound examination may reveal moderate midline shift toward the unaffected side. In frontal pole, frontal base, or bifrontal tumors, there may be no midline shift, but varying degrees of tumor pathological waves can be observed. Tumor compression of the foramen of Monro causing obstructive hydrocephalus may show increased ventricular wave amplitude and an increased distance between the lateral ventricular wave and midline wave, which can be used to estimate the degree of hydrocephalus.

5. Electroencephalogram (EEG) The EEG findings of frontal lobe tumors exhibit the following characteristics: (1) The occurrence rate of localized δ waves is relatively high, approximately 83%; (2) 40% of cases present with unilateral or bilateral paroxysmal monorhythmic δ waves, particularly more common in tumors of the medial or basal surfaces of the frontal lobe; (3) In unilateral frontal lobe tumors, about one-third show propagated δ waves on the contralateral frontal region, though generally with lower amplitude, often forming mixed δ waves. The background α waves appear normal in one-third of cases. Generally, the more anterior the tumor location, the milder the α wave abnormalities; (4) Bilateral frontal lobe tumors are characterized by the appearance of independent polymorphic δ waves in both frontal regions, more pronounced on the side with the larger tumor. θ waves and lazy waves appear over a broader range.

6. Brain CT Examination CT primarily diagnoses intracranial tumors through the contrast in density between the tumor and surrounding tissues, as well as the displacement and deformation of normal structures (such as the ventricles). Frontal lobe tumors are commonly gliomas and meningiomas, generally showing higher density; the anterior horn of the lateral ventricle is often compressed and deformed.

bubble_chart Differentiation

Frontal lobe tumors generally progress relatively slowly, with mild early clinical symptoms. As the tumor continues to grow, clinical manifestations gradually increase and worsen. Based on detailed medical history inquiries and thorough comprehensive examinations, it is important to differentiate them from other intracranial diseases that can cause symptoms similar to those of frontal lobe tumors.

(1) Subdural hematoma: Frontal lobe subdural hematoma is a common clinical condition that can occur at any age, often with a clear history of trauma. Symptoms of increased intracranial pressure appear shortly after the injury or within months, with limited signs being less obvious but psychiatric symptoms more pronounced. A few patients may experience epileptic seizures. Especially in chronic or subacute subdural hematomas, clinical differentiation from tumors is difficult, often requiring angiography and CT scans for a definitive diagnosis. In carotid angiography for frontal lobe subdural hematomas, the anterior cerebral artery shows an arcuate shift to the opposite side in the anteroposterior view, while the middle cerebral artery is depressed and shifted medially to varying degrees. A crescent-shaped avascular area is often visible between the vessels and the inner table of the skull. CT is highly useful for localizing hematomas.

(2) Frontal lobe abscess: The clinical symptoms and signs of frontal lobe abscesses are largely similar to those of tumors. However, brain abscesses often result from infections elsewhere in the body, with an acute onset and a history of fever. Peripheral blood and cerebrospinal fluid often show elevated polymorphonuclear leukocytes. In the capillary-venous phase of carotid angiography, about 50% of brain abscesses display a uniform radiopaque wall, which can be considered a characteristic feature. CT scans of brain abscesses reveal clearly defined low-density areas, whereas tumors typically show high-density areas, making differentiation easier. However, a few brain abscesses may be difficult to distinguish from tumors preoperatively, requiring surgical exploration for confirmation.

(3) Craniopharyngioma: Craniopharyngiomas are more common in school-aged children and young adults under 20, rarely seen in adults, whereas frontal lobe tumors are more common in adults. The initial symptoms of craniopharyngioma often involve endocrine dysfunction, with growth retardation in children and hypogonadism in adults. Frontal lobe tumors lack these symptoms, with early manifestations typically being psychiatric disorders, whereas psychiatric symptoms in craniopharyngioma patients are rare and mild. Frontal lobe tumors often cause papilledema without early visual impairment, but advanced stages may lead to secondary optic atrophy and vision loss. Craniopharyngiomas frequently present with primary optic atrophy and early visual impairment. Craniopharyngiomas often exhibit eggshell-like calcifications in the suprasellar or intrasellar regions, accompanied by changes in the shape and bone structure of the sella turcica. Frontal lobe tumors rarely show calcification, and the few that do lack the typical location and appearance seen in craniopharyngiomas.

(4) Pituitary tumors: Pituitary adenomas are more common in adults, with main symptoms including pituitary dysfunction, bitemporal hemianopia, headache, and primary optic atrophy. Some patients may present with acromegaly, and the sella turcica often shows spherical enlargement, making diagnosis straightforward. However, when large tumors extend into the suprasellar region, patients may exhibit psychiatric symptoms and epileptic seizures. If the tumor affects the internal capsule, cerebral peduncle, or compresses the anterior or right cerebral arteries, impairing blood circulation, hemiplegia may occur, necessitating differentiation from frontal lobe tumors. Additionally, tumors at the base of the frontal lobe often cause visual and field changes, which should also be distinguished from pituitary tumors.

(5) Olfactory Groove Meningioma Olfactory dysfunction and mental abnormalities are the main clinical features of olfactory groove meningioma. Additionally, headache, visual impairment, and epileptic seizures are also common symptoms. Frontal lobe tumors rarely present with olfactory or visual disturbances, except for a few tumors located at the base of the frontal lobe. Skull radiographs of olfactory groove meningiomas often reveal abnormal bone structure in the anterior cranial fossa or tumor calcification. Bilateral carotid angiography primarily shows vascular displacement of the anterior cerebral arteries. On lateral images, the anterior cerebral artery appears as an upwardly curved arc, with an increased distance between the vessels and the floor of the anterior cranial fossa. The frontal polar artery forms an upwardly arched curve. Displacement of the middle cerebral artery is minimal or nearly normal. The supraclinoid segment of the internal carotid artery may tilt slightly backward, sometimes shifting posteriorly, causing the siphon segment to become distorted. On lateral images, compression of the orbital roof artery with downward displacement is often observed. Based on these characteristics, differentiation from frontal lobe tumors is straightforward.

(VI) Sellar tubercle meningioma. The initial symptoms are mostly visual disturbances, followed by headache. In advanced stages, endocrine disorders may occur, along with symptoms such as drowsiness, olfactory hallucinations, and anosmia. In adults, if unilateral or bilateral temporal hemianopia occurs, with primary optic nerve atrophy and no significant changes in the sella turcica, sellar tubercle meningioma should be suspected. Differentiation from tumors at the base of the frontal lobe should be noted.

(VII) Lateral ventricle tumors. Lateral ventricle tumors are relatively rare. Clinical symptoms vary depending on the tumor's location and size. The initial symptom is often headache, which may be intermittent or paroxysmal and worsen over time. In severe cases, nausea, vomiting, and visual disturbances may occur. Patients also frequently experience epileptic seizures and motor impairments in the limbs. Cranial ultrasound and EEG examinations show space-occupying lesions in one cerebral hemisphere in 90% of cases. Ventriculography and cerebral angiography have diagnostic value for localization and characterization, making differentiation from frontal lobe tumors easier.

(VIII) Frontal lobe tuberculoma. The frontal lobe is one of the common sites for tuberculomas. The clinical symptoms are very similar to those of frontal lobe tumors. Tuberculomas often have a history of tuberculosis, low-grade fever, and an accelerated erythrocyte sedimentation rate. A few patients may exhibit characteristic cerebrospinal fluid changes due to accompanying tuberculous meningitis. However, many frontal lobe tuberculomas can only be definitively diagnosed during surgical exploration.

(IX) Cerebrovascular diseases. Common vascular diseases in the frontal lobe include cerebrovascular malformations and intracranial aneurysms.

1. Frontal lobe cerebrovascular malformations. These are mostly distributed in the areas supplied by the middle cerebral artery and the anterior cerebral artery. Hemorrhage and epileptic seizures are often the initial symptoms of cerebrovascular malformations. Headache, progressive neurological dysfunction, and intellectual decline are also common. A few patients may hear intracranial vascular murmurs near the eyes or forehead. CT scans typically show lesions with isodensity surrounded by low-density areas. Intracranial hemorrhage may appear as corresponding high-density areas. Subarachnoid hemorrhage may also be visible. After contrast enhancement, the vascular lesion area may appear as high-density, sometimes revealing the supplying artery and draining veins. Cerebral angiography is the primary basis for differentiating cerebrovascular malformations from intracranial tumors.

2. Intracranial aneurysms. These mostly occur in the circle of Willis and its major branches, with 85% located in the anterior half of the internal carotid artery system. About 90% of aneurysm patients present with subarachnoid hemorrhage, manifesting as sudden severe headache accompanied by nausea, vomiting, photophobia, pallor, neck stiffness, and a positive Kernig's sign. Severe cases may exhibit impaired consciousness or psychiatric symptoms. Others may develop unilateral weakness due to hemorrhage extending into one hemisphere, which gradually worsens. Some patients may experience slowly rising intracranial pressure due to impaired reabsorption of cerebrospinal fluid by arachnoid granulations, leading to prolonged headache and gradually worsening papilledema. These patients should undergo further examinations (EEG, ultrasound, or even cerebral angiography or CT scans) to rule out tumor-related hemorrhage or hematoma formation.

(X) Intracranial paragonimiasis. Frontal lobe paragonimiasis often causes epileptic seizures and psychiatric symptoms. Clinically, it resembles tumors, but differentiation from frontal lobe tumors is not difficult based on epidemiology, history of paragonimus contact, presence of paragonimus in other parts of the body, positive skin tests, and complement fixation tests in blood and cerebrospinal fluid.