Neoplastic lesions of the brain

*Read from printed notes – Ian Brown

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Notes from emedicine.com

Background

• Brain tumors may originate from neural elements within the brain, or they may represent spread of distant cancers.
• Primary brain tumors arise from CNS tissue
• account for roughly half of all cases of intracranial neoplasms
• The remainder of brain neoplasms are caused by metastatic lesions.
• In adults, two thirds of primary brain tumors arise from
• structures above the tentorium (supratentorial)
• In children, two thirds of brain tumors arise from structures below the tentorium (infratentorial).
• 95% of brain tumours
• Gliomas
• Low grade
• Astrocytoma
• common in young people
• High grade
• Anaplastic astrocytoma
• Gliobastoma multiforme
• metastases
• meningioma
• pituitary adenoma
• acoustic neuroma
• Classification by tumor cell type is irrelevant to the emergency physician because emergent treatment is the same regardless of the tumor type.

Pathophysiology

• Tumors of the brain produce neurologic manifestations through a number of mechanisms
• Small, strategically located tumors may damage specific neural pathways traversing the brain
• Tumors can invade, infiltrate, and supplant normal parenchymal tissue, disrupting normal function.
• Because the brain dwells in the relatively restricted repository of the cranial vault, growth of intracranial tumors with accompanying edema may compress normal tissue and impair function
• Space-ocupying lesion
• May manifest vision problems, and headaches
• Tumors proximal to the third and fourth ventricles
• may obstruct the flow of cerebrospinal fluid
• leading to hydrocephalus
• In addition, tumors generate new blood vessels (ie, angiogenesis)
• disrupting the normal blood-brain barrier
• causing edema
• The cumulative effects of tumor invasion, edema, and hydrocephalus may elevate the intracranial pressure (ICP)
• impair cerebral perfusion
• Intracranial compartmental rise in ICP may provoke shifting or herniation of tissue
• under the falx cerebri
• through the tentorium cerebelli OR
• through the foramen magnum
• Slow-growing tumors
• particularly tumors expanding in the so-called silent areas of the brain
• such as the frontal lobe
• may be associated with a more insidious course
• These tumors tend to be larger at detection
• Most primary brain tumors do not metastasize
• Of those neural element tumors that do
• intraparenchymal metastasis generally precedes distant hematogenous dissemination via the arterial system
• Metastatic brain tumors from non-CNS primary tumors may be the first sign of malignancy
• or they may herald a relapse.
• Nonetheless, the signs and symptoms of brain metastases simulate those of primary brain tumours

Diagnosis

History

• headache
• altered mental status
• memory loss and decreased alertness
• suspect: frontal lobe tumour
• depersonalization, emotional changes, and behavioral disturbances
• Temporal lobe neoplasms
• increased irritability, unsteadiness, ataxia, headache, vomiting, and progressive obtundation
• paedetric posterior fossa tumour
• ataxia
• nausea & vomiting
• weakness & gait disturbance
• Sensory disturbance
• vision
• smell
• hearing
• intermittent (then progressive) hearing loss, disequilibrium, and tinnitus
• acoustic neuroma
• focal seizures, fixed visual changes, speech deficits, or focused sensory abnormalities
• onset of symptoms usually is insidious, but an acute episode may occur with
• bleeding into the tumor, or
• when an intraventricular tumor suddenly occludes the third ventricle
• seizures, hemiparesis, visual field cuts, speech difficulties, and intellectual disturbance.
• Supratentorial tumors in children
• Pituitary adenoma
• Non-functional
• when large enough can compress optic chiasma
• causing vision problems
• Hypersecretory
• secrete prolactin
• women
• amenorrhea-galactorrhea syndrome
• men
• impotence

Physical examination

• Increased Intracranial pressure
• papillaedema
• Diplopia
• compression/displacement of 6th CN
• at base of brain
• Impaired upward gaze (Parinaud syndrome)
• may occur with pineal tumours
• Homonymous hemianopia
• tumour of occipital lobe
• Anosmia
• frontal lobe tumours
• Brainstem and cerebellar tumors
• cranial nerve palsies
• ataxia
• incoordination
• nystagmus
• pyramidal signs
• sensory deficits
• Facial, cochlear, and vestibular CN dysfunction
• run through the cerebellopontine angle
• Vestibular nerve
• acoustic neuroma

Imaging studies

• CT
• Intravenous contrast
• for tumour idenfication
• May appear
• hypodense
• isodense
• hyperdense
• MRI
• helpful in identifying
• tumours in posterior fossa
• including acoustic neuroma
• haemorrhagic lesions
• Xray
• tumour on sella turcica
• pituitary tumour/adenoma
• Lumbar puncture
• not needed

Complications

• Acute hemorrhage into a tumor
• Brain neoplasms predisposed to hemorrhage include lung cancer, melanoma, and choriocarcinoma.
• Lesions near the third ventricle can cause
• paroxysmal symptoms of headache, syncope, or mental status change.
• vomiting, ataxia, memory changes, visual disturbances, or personality change
  s may occur
• Episodic increases in ICP
• secondary to pressure arising from blockage of cerebrospinal fluid outflow
• Sudden death
• obstruction of outflow drainage from the third ventricle
• Sudden increases in ICP
• may lead to life-threatening brain herniation
• shifts the brain parenchyma in the direction of least resistance:
• caudally through the foramen magnum (posterior fossa tumors) or
• transtentorial apertures.
• Some pituitary tumors are hormonally active
• acromegaly
• galactorrhea

Treatment

Prehospital Care

• Supportive
• Airway disturbance
• breathing difficulty
• Signs of pronounced elevation in ICP
• Impairment of consciousness
• May necessitate definitive airway control with endotracheal intubation
• Hyperventilation.

Emergency Department Care

• Corticosteroids
• may dramatically reduce signs and symptoms related to cerebral edema
• experience relief within the first few hours of steroid therapy
• Dexamethasone
• agent of choice
• minimal salt-retaining properties
• For patients with signs or symptoms of impending herniation and airway compromise
• consider use of adjunctive medications for rapid sequence intubation
• These might include lidocaine and medication for rapid-onset neuromuscular blockade, with precautions to diminish fasciculations
• Induction agents, such as thiopental, may be used
• After definitive control of the airway,
• consider gentle hyperventilation
• Mannitol
• Hyperosmolar agent
• Reduce ICP & cerebral oedema
• creating an osmotic gradient across an intact blood-brain barrier
• between cerebrospinal fluid in arachnoid space and blood plasma
• May have rebound
• Increases in ICP
• makes its use problematic

Surgical intervention/Radiotherapy

• Tumour resection/debulking
• Installation of ventricular shunt
• Placement of radioactive implants