BRAIN TUMORS
Because the brain is encased in a nonexpandable bony skull, both benign and malignant brain tumors can cause death if not appropriately diagnosed and treated. Brain tumors cause elevated intracranial pressure (ICP) by occupying space, producing cerebral edema, interfering with the normal flow of cerebrospinal fluid, or impairing venous drainage (Fig. 20-1). Patients may present with progressive neurologic deficits owing to increasing ICP, tumor invasion, or brain compression. Alternatively, they can present with headache or seizures.
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Figure 20-1 • Pathways for the circulation of cerebrospinal fluid. |
PATHOLOGY
Intracranial tumors can be classified as either intra-cerebral or extracerebral (Table 20-1). Intracerebral tumors include glial cell tumors (astrocytomas, oligodendrogliomas, ependymomas, primitive neuroectodermal tumors), metastatic tumors (lung, breast, skin [melanoma], kidney, colon), pineal gland tumors, and papillomas of the choroid plexus. Extracerebral tumors arise from extracerebral structures and include meningiomas, acoustic neuromas, pituitary adenomas, and craniopharyngiomas.
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TABLE 20-1 Intracranial Tumors |
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Glial cell tumors and metastatic tumors are the most common central nervous system (CNS) tumors seen in adults. Children have a higher proportion of posterior fossa tumors.
GLIAL CELL TUMORS
Glial cells account for approximately 50% of CNS tumors in adults. Different glial cell types (astrocytes, oligodendrocytes, ependymal cells, and neuroglial precursors) give rise to various histologic types of tumors. Although the term "glioma" can be used to describe the above glial tumor types, its common use refers only to astrocytic tumors.
Astrocytic tumors are graded I to IV based on histologic evidence of malignancy; grade I and II tumors are slow-growing malignancies. In children, astrocytomas located in the posterior fossa (cerebellum) usually have cystic morphologies (pilocystic astrocytoma). Grade III tumors are the more aggressive anaplastic astrocytomas. The most common as well as the most malignant astrocytoma is the grade IV glioblastoma multiforme. Glioblastoma multiforme tumors often track through the white matter, crossing the midline via the corpus callosum, resulting in the so-called butterfly glioma on computed tomography (CT). Median survival is 1 year.
Oligodendrogliomas are slow-growing calcified tumors, often seen in the frontal lobes. They are most common in adults and are often associated with seizures.
Ependymomas arise from cells that line the ventricular walls and central canal. Clinical signs and symptoms of elevated ICP are the main features of presentation. Ependymomas are mostly seen in children and usually arise in the fourth ventricle.
Classified by location, infratentorial posterior fossa tumors make up most of the lesions seen in childhood. These are most commonly cystic cerebellar astrocytomas, ependymomas, and medulloblastomas. Highly malignant medulloblastomas typically occur in the vermis in children and in the cerebellar hemispheres in young adults.
METASTATIC TUMORS
Approximately 30% of patients with systemic cancer have cerebral metastases, which usually originate in the lung, breast, skin (melanoma), kidney, and colon. Most lesions are supratentorial and located at the cortical
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white matter junction. Resection depends on the nature of the underlying malignancy, symptoms, and prognosis. Single, approachable lesions should be considered for surgical resection in the appropriate setting. Radiation usually follows surgery. Stereotactic radiosurgery is an option in patients with multiple lesions.
MENINGIOMAS
Slow-growing, meningiomas arise from the meninges lining the brain and spinal cord. Complete tumor removal is curative, and residual disease can be observed or treated with radiosurgery.
History
Patients usually present with neurologic signs and symptoms attributable to cerebral compression from the expanding tumor mass. Seizures are a common presentation. Headache, nausea, vomiting, and mental status changes are the most common generalized symptoms of elevated ICP. Classically, patients complain of diffuse headache that is worse in the morning after a night of recumbency.
Physical Examination
Bilateral papilledema may occur, especially in the later stages of disease. Personality changes may be
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noted early on and may progress to stupor and coma as ICP increases and brain herniation occurs (Fig. 20-2). Speech deficits and confusion are common with dominant hemisphere lesions. Eye deviation can be a sign of frontal lobe involvement. Ataxia is common with cerebellar tumors. Motor or sensory deficits indicate involvement around the central sulcus or deep structures, especially if combined with mental status changes.
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Figure 20-2 • Examples of brain herniation: (1) cingulate gyrus herniation across the falx; (2) temporal uncus herniation across the tentorium; (3) cerebellar tonsil herniation through the foramen magnum; (4) herniation of brain tissue through craniotomy defect. |
Differential Diagnosis
The differential diagnosis for a patient presenting with central neurologic deficits and symptoms includes cerebrovascular accident, neurodegenerative diseases, abscess, vascular malformations, meningitis, encephalitis, communicating hydrocephalus, and toxic state.
Diagnostic Evaluation
CT and magnetic resonance imaging (MRI) assist in making the diagnosis and in localization of the tumor. MRI with gadolinium enhancement is useful for visualizing higher-grade gliomas, meningiomas, schwannomas, and pituitary adenomas. T2-weighted MRI is useful for low-grade gliomas.
Treatment
Correct management of primary brain tumors requires knowledge of the natural history of specific tumor types and the risks associated with surgical removal. When feasible, total tumor removal is the goal; however, subtotal resection may be necessary if vital brain function is threatened by complete tumor extirpation. If subtotal resection is performed, postoperative radiation therapy can prolong life and palliate symptoms. Chemotherapy is also used for specific tumor types.
Metastatic brain tumors are generally treated with whole-brain irradiation. Occasionally, single lesions amenable to surgery are removed first, followed by whole-brain irradiation.
Perioperative management of increased ICP caused by cerebral edema is accomplished by using corticosteroids (dexamethasone [Decadron]). If hydrocephalus is present, shunting of cerebrospinal fluid may be required.
INTRACRANIAL ANEURYSMS
Intracranial aneurysms are saccular, berry-shaped aneurysms, usually found at the arterial branch points within the circle of Willis (Fig. 20-3). Although they
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rarely rupture, significant morbidity and mortality may result secondary to hemorrhage. Subarachnoid hemorrhage (SAH) develops when intracranial aneurysms rupture and bleed.
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Figure 20-3 • Cerebral arterial circle of Willis. |
HISTORY
Sudden onset of a severe headache, typically described as the "worst headache of my life," usually signals the rupture of an intracranial aneurysm. ICP transiently increases with each cardiac contraction, causing a pulsating headache. Progressive neurologic deficits may develop as a result of blood clot mass effect, vasospasm with infarction, or hydrocephalus. Coma and death may occur.
A system for categorizing the severity of hemorrhage has been developed using clinical assessment based on neurologic condition. The five-point Hunt-Hess grading system ranges from grade 1, indicating good neurologic condition, to grade 5, indicating significant neurologic deficits (Table 20-2).
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TABLE 20-2 Hunt-Hess Classification of Subarachnoid Hemorrhage |
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DIAGNOSIS
CT is useful for demonstrating SAH. If CT is negative in a patient with a highly suspicious presentation, a lumbar puncture should be performed. If SAH is present, four-vessel cerebral angiography is performed to define the aneurysm neck and relationship with surrounding vessels (Fig. 20-4).
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Figure 20-4 • A vertebral artery angiogram is shown in A; the same view, but in a different patient, is shown in B, using digital subtraction methods. Relevant arteries are labeled. From Haines DE. Neuroanatomy: An Atlas of Structures, Sections, and Systems. 6th ed. Philadelphia, PA: Lippincott Williams & Wilkins, 2004. |
TREATMENT
Initial medical treatment involves control of hypertension with intravenous medications. Phenytoin is administered for prophylactic treatment of seizures, mannitol can be given to control edema, and nimodipine is used to reduce the risk of developing delayed neurologic deficits from vasospasm.
Emergency external ventricular drainage may be indicated to decrease the ICP. In rare cases with progressive neurologic deterioration, emergency crani-otomy and evacuation of a blood clot are required to prevent herniation. The definitive treatment is obliteration by microsurgical clipping or endovascular coiling of the aneurysm.
EPIDURAL HEMATOMA
Epidural hematomas are usually seen in patients with head trauma who have sustained a skull fracture across the course of the middle meningeal artery, causing an arterial laceration and an expanding hematoma (Fig. 20-5). The increasing pressure of the arterial-based hematoma strips the dura mater from the inner table of the skull, producing a lens-shaped mass capable of causing brain compression and herniation.
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Figure 20-5 • Epidural hemorrhage: epidural hematoma. This 8-year-old boy presented after a sledding accident. He had no loss of consciousness but complained of headache and vomiting. A head computed tomography scan shows the classic biconvex hyperdensity of an epidural hematoma. From Fleisher GR, Ludwig S, Baskin MN. Atlas of Pediatric Emergency Medicine. Philadelphia, PA: Lippincott Williams & Wilkins, 2004. |
HISTORY
The presentation of an epidural hematoma is commonly described as a head injury followed by an initial loss of consciousness, recovery (the honeymoon period), and then progressive deterioration. In reality, this sequence of events is unusual. It is more common not to have an initial period of unconsciousness or to become unconscious initially and not to regain it.
PHYSICAL EXAMINATION
Assessing the level of consciousness is the most important aspect in evaluating head injuries. The standard clinical tool for assessment is the Glasgow Coma Scale (GCS), which evaluates eye opening, verbal response, and motor response. Patients with a GCS of ≤7 have severe head injuries, those with scores of 8 to 12 have moderate injuries, and those with scores of >12 have mild injuries. Patients with severe injuries (GCS <8) require immediate endotracheal intubation for airway protection and rapid neurosurgical evaluation (Table 20-3).
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TABLE 20-3 Calculation of Glasgow Coma Score |
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DIAGNOSTIC EVALUATION
CT is crucial to establish a diagnosis and treatment plan.
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TREATMENT
For patients presenting with a depressed skull fracture and a neurologic examination indicating a deteriorating level of consciousness, airway control and emergency cranial decompression must be performed. Burr holes are made over the area of hematoma seen on CT, a flap is quickly turned, and the clot is decompressed, with resultant decrease of the ICP. Middle meningeal artery bleeding is controlled, and the dura is fixed to the bone to prevent reaccumulation.
SUBDURAL HEMATOMA
In contrast with epidural hematomas, subdural hematomas are usually low-pressure bleeds secondary to venous hemorrhage. Both spontaneous and traumatic subdural bleeds occur. The source of hemorrhage is from ruptured bridging veins that drain blood from the brain into the superior sagittal sinus.
RISK FACTORS
Most commonly, subdural hematoma is a result of trauma. Older adult patients, those with brain atrophy, and patients treated with anticoagulants are at particularly increased risk. Less common causes include rupture of a cerebral aneurysm, arteriovenous malformation, and metastatic tumors.
HISTORY
Headache, drowsiness, and unilateral neurologic symptoms are the usual presenting symptoms. Seizure activity and papilledema are uncommon.
EVALUATION
Prompt imaging is the cornerstone of diagnosis. Head CT should be performed in patients with the appropriate history. MRI is more sensitive and may be considered. In patients without history of trauma, angiography may be useful to identify the root cause.
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TREATMENT
Nonoperative management is limited to patients who are stable, have small lesions, and do not have evidence of herniation. Patients with significant neurologic deficits secondary to mass effect may need urgent burr-hole decompression or craniotomy. Other indications for surgical management include lesion size >10 mm, >5 mm of midline shift, or declining GCS. Generally, it is important to identify and ligate the bleeding vessel.
SPINAL TUMORS
Tumors are defined by anatomic location as being extradural, intradural, or intramedullary (Fig. 20-6). Extradural tumors are most commonly lesions of metastatic disease from primary cancers of the lung, breast, or prostate. Other common tumors are multiple myeloma of the spine and lymphoma. Back pain or neurologic deficit from cord compression is the usual presenting complaint.
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Figure 20-6 • Topographic distribution of the common neoplasms of the spinal meninges, spinal nerve roots, and spinal cord. |
The most common intradural tumors are meningiomas, schwannomas, neurofibromas, and ependymomas. A nerve root tumor may transverse the intervertebral foramen, forming a bilobed lesion called a dumbbell tumor. Patients usually present with numbness progressing to weakness.
Intramedullary tumors include astrocytomas, ependymomas, and cavernous malformations. It is important to differentiate cystic tumors from syringomyelia by gadolinium-enhanced MRI, because both may present with sensory loss.
DIFFERENTIAL DIAGNOSIS
The differential diagnosis for patients presenting with signs and symptoms of spinal cord pathology are cervical spondylitic myelopathy, acute cervical disc protrusion, spinal angioma, and acute transverse myelitis.
PHYSICAL EXAMINATION
Patients with tumors of the spine typically present with complaints indicative of progressive spinal cord compression, with evidence of a sensory level.
DIAGNOSTIC EVALUATION
Plain radiographs may demonstrate bony erosion. MRI is the modality of choice, because it provides detailed anatomic definition. A CT myelogram may be performed if MRI is unavailable.
TREATMENT
The goal of spinal tumor treatment is to relieve cord compression and to maintain spinal stability. These are interrelated goals, because removing a compressing tumor usually requires surgery on the vertebral column.
The spine consists of two columns: the anterior column (vertebral bodies, discs, and ligaments) and the posterior column (facet joints, neural arch, and ligaments). Damage sustained to one of the columns may result in permanent spinal instability.
For anterior tumors that involve the vertebral body, tumor removal via the anterolateral approach is performed. The vertebral body is resected and the defect repaired with a bone graft and metal plate stabilization.
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Posterior tumors can be removed by laminectomy that usually does not cause spinal instability. Metastatic and unresectable disease can be palliated and pain controlled with radiation therapy. Occasionally, anterior and posterior approaches are combined; therefore, appropriate spine stabilization requirements must be anticipated.
SPONDYLOSIS AND DISC HERNIATION
Degenerative changes in the spine are responsible for a large proportion of spine disease. Intervertebral discs consist of two parts: the central nucleus pulposus, which acts as a cushion between vertebrae, and the surrounding dense annulus fibrosus (Fig. 20-7). At birth, the nucleus contains 80% water, but over time the disk dehydrates, and the disc space narrows. In the cervical and lumbar spines, this narrowing causes abnormal vertebral stresses, which in turn cause osteogenesis, producing osteophytes and bony spurs. These degenerative bone growths can traumatize nerve roots. This degenerative process secondary to abnormal motion in an aging spine is called spondylosis.
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Figure 20-7 • Intervertebral disc: annulus fibrosus and centrally located nucleus pulposus. |
Structural failure of the intervertebral disc occurs when the nucleus pulposus herniates into the spinal canal or the neural foramina through a defect in the circumferential disc annulus. Lateral disc herniation can cause nerve root compression and radicular symptoms; central disc herniation can cause myelopathy.
These two interrelated degenerative processes are responsible for most spine disease, manifested by nerve root and spinal cord compression. The most mobile segments of the spine (cervical and lumbar) are commonly affected by both processes (Fig. 20-8).
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Figure 20-8 • (A) Normal disc space with normal rotatory movement of one vertebra on the adjacent one. (B) Disc protrusion. (C) Osteophytes developing secondary to disc degeneration (or disc protrusion). Note the different origin of the disc protrusion and osteophytes. |
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CERVICAL DISC DISEASE
HISTORY
Patients with cervical spondylosis and disc disease are typically older than 50 years and can present with pain, paresthesia, or weakness. In the case of cervical spondylotic myelopathy secondary to repetitive spinal cord damage by osteophytes, patients experience progressive numbness, weakness, and paresthesia of the hands and forearms in a glove-like distribution. In contrast, patients with radiculopathy secondary to disc disease complain of pain radiating down the arm in a nerve root distribution, worsening on neck extension.
PHYSICAL EXAMINATION
Limitation of neck motion and straightening of the normal cervical lordosis are common findings. Sensory and motor deficits in a radicular pattern and careful testing for signs of diminished biceps, brachioradialis, and triceps reflexes assist with localization. Hyperreflexia and the presence of the Hoffmann (reflex contraction of thumb and index finger on tapping the nail of or flicking the middle finger) or Babinski reflex (extension of the great toe on stroking the lateral aspect of the sole of the foot) help determine the presence of myelopathy and are important signs to elicit.
DIFFERENTIAL DIAGNOSIS
All causes of cervical spinal cord or cervical nerve root compression must be considered. More common causes of cord compression are rheumatoid arthritis and ankylosing spondylitis. For nerve root compression, brachial plexus compression from a first or cervical rib and scalenus anticus syndromes (thoracic outlet syndrome) should be ruled out. Peripheral nerve entrapment (carpal tunnel syndrome, ulnar nerve palsy) and Pancoast tumor of the pulmonary apex should be considered in patients who have arm pain without neck pain.
Diagnostic Evaluation
Cervical spine x-rays show straightening of the normal cervical lordosis, disc space narrowing, osteophyte formation, and spinal canal narrowing. If the axial diameter of the cervical spinal canal is ≤10 mm, risk is high for cervical cord compression.
CT myelography and MRI are used to evaluate the spinal cord and nerve roots and define their relationships to other vertebral structures. Areas of cord and root compression can be identified and intervention planned. MRI is the study of choice for initial evaluation of a herniated cervical disc, whereas CT is preferred when more bony detail is required.
TREATMENT
All patients should initially be managed with medical therapy, except for those with myelopathy or severe radicular weakness. Cervical traction, analgesics, and muscle relaxants are used. For acute cervical radiculopathy caused by cervical disc herniation, >95% of patients improve without surgery. However, patients with spondylosis and disc prolapse who fail to improve or who exhibit progressive worsening may require surgical treatment.
Because the pathogenesis of degenerative osteogenesis is abnormal stress and movement between vertebrae, procedures aimed at stabilizing the spine have shown significant success in obtaining symptomatic relief and promoting osteophyte reabsorption. Anterior cervical fusion produces immobilization by removal of the intervertebral disc, with bone graft replacement and internal fixation. Both cervical spondylosis and cervical disc prolapse can be treated with this procedure.
Decompression laminectomy is usually performed only on patients who have a diffusely narrow spinal canal and who are rapidly worsening as a result of spondylotic myelopathy. The posterior approach for lateral disc herniations is also used to avoid segmental fusion.
LUMBAR DISC DISEASE
Lumbar disc prolapse is a common disorder. Patients often present with pain radiating down the lower extremity.
PHYSICAL EXAMINATION
Symptoms of sciatica are caused by disc herniation compressing a nerve root, leading to severe radicular pain. The L4-5 and L5-S1 discs most commonly prolapse, leading to L5 and S1 nerve root symptoms. Paresthesia, numbness, and weakness may be present.
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Straight leg raise testing can be positive for pain radiating down the affected extremity, with both ipsilateral and contralateral leg raising. Other important signs indicating disc herniation include absence of an ankle or knee reflex, weakness of foot dorsiflexion or plantar flexion, or weakness of knee extension.
DIAGNOSIS
Clinical diagnosis is confirmed by MRI that demonstrates disc protrusion at the suspected level (Fig. 20-9).
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Figure 20-9 • The relations of a lumbar disc prolapse. The protruding disc causes nerve root compression. |
TREATMENT
Most patients improve without surgery. Elective surgery should be considered for patients with chronic, disabling, intractable pain. The standard procedure of choice is open laminectomy and discectomy of the appropriate interspace. Urgent surgery is indicated in patients with progressive neurologic deficits (e.g., foot drop) and in those with acute onset of cauda equina syndrome, which is a neurosurgical emergency and occurs as a result of a massive midline disc protrusion that compresses the cauda equina. Typical findings of cauda equina syndrome include urinary retention or overflow incontinence, bilateral sciatica, and perineal numbness and tingling (i.e., saddle anesthesia). Bilateral laminectomy decompression with disc removal is the procedure of choice.
KEY POINTS
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