Brain Tumors: Types and Definitions

Brain Tumors Definition

• Space-occupying lesions (SOLs) exist within the cranial cavity.
• SOLs give rise to increased intracranial pressure.
• SOLs cause focal cranial manifestations depending on lesion site.

Pathological Types of Brain Tumors

• Neoplastic tumors include primary and secondary (metastatic) brain tumors.
• Non-Neoplastic tumors include brain abscesses, tuberculomas, and parasitic cysts.

Neoplastic SOL Primary Tumors

• Primary tumors arise from various structures.
• Bone tumors can be osteomas or osteosarcomas.
• Meninges tumors can be meningiomas or meningiosarcomas.
• Glial cells can be gliomas, astrocytomas (G 1-4), or glioblastoma multiforme.
• Ependymal cells can form ependymomas.
• Pituitary gland tumors include adenomas and adenocarcinomas.
• Embryonic remnants can lead to craniopharyngiomas, chordomas, and medulloblastomas.
• The pineal gland can develop pinealomas.
• Cranial nerves can give rise to neuromas like Schwannomas (e.g., acoustic or trigeminal neuroma).
• The choroid plexus can form choroid plexus papillomas.

Metastatic Tumors

• Metastatic tumors are not rare, especially in old age.
• Metastatic tumors are commonly multiple and bilateral.
• A solitary cerebellar lesion in old age is often metastatic.
• Common primary tumor sites for brain metastasis include the breast, kidneys, thyroid, GIT, and testis.

Brain Abscess

• Brain abscesses are non-neoplastic SOLs.

Clinical Picture of Brain Tumors

• Brain tumors present in three ways: manifestations of increased intracranial tension, focal cranial manifestations, or both.

Manifestations of Increased Intracranial Pressure (ICP)

• Increased ICP can cause headache, nausea/vomiting, blurring of vision, hypertension, and bradycardia.
• VI nerve palsy can be a false localizing sign due to increased ICP affecting the long, thin nerve.

Headache

• Headaches are severe.
• Headaches can be throbbing, bursting, or dull-aching.
• Headaches may be frontal, temporal, or generalized.
• Headache location does not correlate with lesion site, except: bitemporal headaches in pituitary tumors and suboccipital headaches in infratentorial tumors.
• Headaches worsen at night due to CO2 accumulation and venous congestion during sleep.
• Straining increases headaches.
• Analgesics and/or diuretics partly relieve headaches.

Pathogenesis of Headache from Brain Tumors

• Brain tumors cause headaches through three mechanisms: increased intracranial tension, pressure on sensory areas (e.g., V cranial nerve), and erosion of skull bones.
• Brain tissue is not sensitive to pain.

Vomiting

• Vomiting usually occurs at the peak of a headache.
• Headache is partly relieved by vomiting.
• Vomiting is not preceded by nausea.
• Vomiting is unrelated to meals.
• Vomiting may be projectile (rare).
• Regular antiemetics do not relieve vomiting.

Pathogenesis of Vomiting

• Vomiting results from congestion of the chemoreceptor trigger zone in the medulla oblongata.
• Vomiting is an early symptom in medulloblastoma.

Blurring of Vision

• Blurring of vision is linked to papilledema (optic disc edema).
• Papilledema arises from venous congestion of the retina/optic disc.

How Brain Tumors Increase ICP

• Mass lesions cause increased ICP.
• Vascular tumors increase cerebral blood flow.
• Increased CSF production occurs with choroid plexus papillomas.
• Obstruction of the CSF pathway leads to hydrocephalus.
• Tumors can cause massive oedema.
• Hemorrhage inside the tumor will elevate pressures.

Focal Cranial Manifestations of Brain Tumors

• Localizing manifestations differ based on tumor site.
• Symptoms are gradual and progressive.

Frontal Lobe Manifestations

• Prefrontal area damage causes mental, memory, cognitive, personality, and behavior changes (deterioration).
• Mood changes may occur.
• Broca's area damage (dominant hemisphere) leads to dysphasia or aphasia (speech, reading, writing deficits).
• Precentral gyrus (motor area) damage causes: Weakness of the opposite side (monoparesis or hemiparesis) and Irritative lesions causing focal motor fits/seizures/epilepsy

Parietal Lobe Manifestations

• Destructive lesions result in cortical sensory loss on the opposite side of the body.
• Irritative lesions can cause focal sensory fits.

Temporal Lobe Manifestations

• Destructive lesions lead to mild affection of smell, taste, and hearing.
• Irritative lesions can cause temporal lobe fits.
• The temporal lobe is the most common site for partial epilepsy.
• Temporal lobe fits are usually partial, with gastric uprising sensation, fear, automatism, lip smacking, stare, and déjà vu phenomena.
• Superior quadrantic crossed homonymous hemianopia is a possible symptom.

Occipital Lobe Manifestations

• Destructive lesions cause crossed homonymous hemianopia with macular sparing.
• Irritative lesions cause visual hallucinations.

Brain Stem Manifestations

• Damage affects cranial nerves (LMNL) and long tract manifestations.

Cerebellum Manifestations

• Truncal ataxia and/or limb ataxia.

Pituitary Gland Tumors

• These tumors can cause secretory hormonal syndromes.
• Non-secretory tumors cause chiasmal compression.
• Chiasmal compression leads to visual deterioration (bitemporal hemianopia), possibly progressing to optic nerve atrophy and blindness.

Investigations for Brain Tumors

• Plain X-ray: Shows separation of sutures and/or "silver beaten" appearance (due to high ICP) and widening of the Sella turcica.
• CT scan brain is useful for detecting most lesions and diagnosing hemorrhage inside a tumor.
• MRI brain (usually with contrast) is the preferred procedure.

Management of Brain Tumors

• Medical management includes dehydrating measures (steroids, diuretics like Lasix and mannitol) and antiepileptic drugs.
• Surgical management varies: ranges from biopsy to partial or complete excision, depending on pathology, lesion location, and surgical setup.