Книги по МРТ КТ на английском языке / Neurosurgery Fundamentals Agarval 1 ed 2019

sinus, or off the vertebral artery. They are a fairly small subtype of AVMs and almost two-thirds occur in women. The most common symptoms at presentation include pulsatile tinnitus, cranial bruit,

and headaches. These lesions are most conveniently classified using angiographic imaging ( Fig. 12.6). Definitive treatment can include endovascular embolization and/or surgery. Endovascular treatment

can utilize coils, Onyx, or ethanol-based compounds with the goal of complete obliteration of arteriovenous shunting on angiogram. Special caution needs to be exercised with surgical intervention due to possibility for large volume blood loss. SRS can also be used with good success rate resulting in complete lesion obliteration in almost 60% of the cases.7

Pearls

•Normal brain at rest requires 45–60 mL of blood flow per 100 g tissue/min.

•Carotid endarterectomy has definite benefit in symptomatic patients with more than 70% stenosis and marginal benefit in those with 50–69% stenosis.

•Trauma is the most common cause of SAH, while aneurysmal rupture accounts for 80% of spontaneous SAH.

•95% of cerebral aneurysms are sporadic rather than due to other causes.

•Anterior circulation is the most common location for aneurysm with ACoA representing 30% of all cases.

•The most common presentation for AVMs is hemorrhage.

•Cavernous malformations are best detected on MRI.

12.5  Top Hits

12.5.1  Questions

1.Which of the following is NOT one of the modifiable risk factors for stroke prevention?

a) Hypertension b) Alcohol consumption c) Lipid levels d) Cigarette smoking e) None of the above

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2.Which of the following therapies could be used in a setting of stroke that occurred 7 hours ago due to a thromboembolus?

a) IV tPA

b) Mechanical thrombectomy c) Intra-arterial tPA

d) IV alteplase

3.Within what time period can IV tPA be utilized to treat vaso-occlusive ischemic stroke?

a) 3 hours b) 3.5 hours c) 4 hours d) 4.5 hours e) 5 hours

4.Occlusion of which artery would result in bilateral thalamic and brainstem stroke?

a) Posterior choroidal artery b) Labyrinthine artery c) Artery of Percheron d) Artery of Heubner

5.What does the Fisher scale predict? a) Risk of mortality after aneurysmal

SAH

b) Risk of mortality and morbidity after aneurysmal SAH

c) Risk of vasospasm in aneurysmal SAH d) Risk of vasospasm in any SAH

6.Which of the following is a major preoperative consideration with aneurysmal clipping?

a) Clipping is not a reasonable alternative to coiling for fusiform aneurysms

b) Mortality and morbidity can be decreased when clipping is

combined with minimally invasive craniotomy approach

c) Intraoperative rupture presents a considerable risk

d) Need for future MRI scans may require coiling rather than clipping

7.Which of the following is true about pipelines or flow diverters?

a) They cannot be used to treat widebased neck aneurysms

b) Their use in treatment of ruptured aneurysms is contraindicated

c) They are not an alternative to stent-coiling

d) Their efficacy has not been well-described

8.In what way is endovascular coiling superior to clipping in treatment of cerebral aneurysms?

a) It is less expensive than coiling b) There is lower chance of

rebleeding

c) Coiling results in lower mortality or dependence than clipping

d) It is more durable than clipping

9.What is the most common location for dural AVM fistulas? a) Transverse sinus

b) Tentorium c) Sigmoid sinus d) Vertebral artery

10.What is the value of angiography in evaluating cavernous malformations? a) It is the gold standard in detecting

these vascular lesions b) It can detect most lesions

c) It is useful in delineating some lesions

d) It cannot be used to detect these lesions

12.5.2  Answers

1.e. All of the listed items are modifiable risk factors for stroke. In addition, antiplatelet therapy has been shown to reduce risk of future events in certain types of strokes.

2.b. According to the HERMES study, treatment with endovascular and medical therapy results in lower disability if treatment is initiated with 7.3 hours

of onset of symptoms.17 At most institutions, patients can be eligible within 8 hours of symptom onset.

3.d. IV tPA has been shown to have clear benefit if given within 4.5 hours of the onset of stroke symptoms.

4.c. Artery of Percheron is a variant in which a single artery arises from PCA to supply both thalami and the midbrain.

5.c. The Fisher scale is used to predict vasospasm risk in aneurysmal SAH based on CT imaging.

6.c. Clipping carries a 20–40% risk of intraoperative rupture. Fusiform aneurysms are better treated with clipping than coiling alone, although combined technique of stent-coiling has proven to be an alternative in treatment of certain aneurysms. Minimally invasive craniotomy aneurysmal clipping has not been proven to have higher efficacy or lower mortality than the typical approaches. Modern clipping techniques utilize MRI-safe titanium clips.

7.b. Pipelines and flow diverters can be used to treat some aneurysms in lieu of stent-coiling.81 Because of the need for antiplatelet and anticoagulation therapy, their use in ruptured aneurysms has generally been limited.59,​78,​79

8.c. Based on data from the ISAT trial, mortality or dependency was lower for coiling than clipping. Rebleeding risk is actually higher in coiling than clipping. Costs appear to be comparable between coiling and clipping, however, the cost of materials in coiling is balanced by longer hospital stays in clipping. Clipping represents a more durable option for treatment. Surgical aneurysm clipping is more expensive than coiling in terms of length of hospital stay and patient costs.

9.a. Transverse sinus is the most common location of dural arteriovenous fistulas.

10.d. Cavernous malformations cannot be detected with cerebral angiography as they are low-flow lesions. They are best evaluated with MRI.

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13.1  Lymphomas and Hematopoietic Tumors

Primary central nervous system lymphoma (PCL) represents extranodal non-Hod- gkin lymphoma that involves the brain, meninges, eyes, and spinal cord. It is a rare entity with approximately four cases per million people per year in the general population. Incidence is 3,600 times higher among patients with AIDS with a lifetime risk of 20% and may be present in up to 10% of patients with AIDS at autopsy.1,​2 Presentation is variable given the large potential area of involvement and may include focal neurologic deficits (70%), neuropsychiatric issues (43%), raised intracranial pressure (ICP) (33%), seizures (14%), ocular involvement (4%).3 Meningeal disease is seen in approximately 40% of patients resulting in cranial neuropathies and headache.4 Ocular involvement is seen in 15 to 25% of patients classically involving the posterior segment of the globe resulting in uveitis, retinal detachment, and retinal/vitreous hemorrhages.3 Over 90% represent high grade, CD20-positive, diffuse large B-cell non-Hodgkin lymphomas. The remainder include Burkitt’s, Burkitt’s-like, lymphoblastic B-cell, and T-cell lymphomas.5 The pathogenesis is incompletely understood as B cells do not typically reside within the central nervous system (CNS) and may involve latent Epstein–Barr virus (EBV) B-cell infection. Lesions are usually periventricular (60%) with variable density and intensity on computed tomography (CT) and T2-weighted magnetic resonance imaging (MRI), respectively. There is homogeneous enhancement including perivascular spaces.6 Mass effect, vasogenic edema, calcification, hemorrhage, cysts, and ring enhancement are often present ( Fig. 13.1).

13.1.1 Diagnosis

Stereotactic needle biopsy is highly specific and is the gold-standard diagnostic modality. If there are no contraindications to lumbar puncture (e.g., mass effect), cerebrospinal fluid (CSF) analysis should be analyzed by cytology, flow cytometry, and polymerase chain reaction (PCR) for immunoglobulin heavy-chain rearrangements. Malignant lymphocytes are present in up to 40% (higher sensitivity with leptomeningeal involvement). CSF typically shows elevated protein and lymphocytic pleocytosis. Glucose concentration may be decreased in cases of leptomeningeal involvement. Histologically, there are large immunoblastic and centroblastic cells with reactive perivascular T-cell infiltrates. Commonly expressed markers include MUM1, BCL6, and BCL2.

13.1.2 Treatment

Surgery is limited to acute reduction of mass effect in the setting of an acute decline. Chemotherapy and radiation are the treatment modalities of choice.

13.1.3 Outcome

Untreated PCL has a mean survival of 1.5years postdiagnosis. However, mean survival after chemotherapy with or without radiation is usually 40 to 50 months, with a 30% 5-year survival rate among immunocompetent adults. Age greater than 60 years, Eastern Cooperative Oncology Group (ECOG) performance status score greater than 1, elevated serum lactate dehydrogenase (LDH), elevated CSF protein, and involvement of deep brain

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regions are negative prognostic factors. Secondary lymphomas occur when systemic lymphomas metastasize to the CNS and is associated with testicular involvement. The cornerstone of management is treatment of the primary disease. Median survival is 2 to 4 months.

13.2  Mesenchymal Tumors

These tumors originate from connective tissue in and about the nervous system and have no neuroectodermal origins per se.

13.2.1 Chordomas

Chordomas (< 1% of intracranial tumors) are destructive, locally aggressive tumors with metastatic potential that arise from persistent rests of fetal notochord. Genetic abnormalities include 1p36 loss, RB mutations, telomerase activation, and

overexpression of platelet-derived growth factor receptor β (PDGFR-β).

Chordomas are hyperintense on T2-weighted imaging (T2WI), isointense on T1WI. Septations, calcification, and a “honeycomb” pattern of enhancement are characteristic features ( Fig. 13.2).

Surgery followed by proton beam radiation is the standard therapy. Chordomas stain positive for brachyury, S-100, cytokeratin, and epithelial membrane antigen (EMA) and may demonstrate bubble-like physaliferous bodies. The 5- and 10-year survival rates of chordoma are approximately 51 and 35%, respectively.8

13.2.2  Chondrosarcomas

Chondrosarcomas (< 0.15% of all intracranial tumors) are indolent bone neoplasms thought to arise from persistent rests of fetal cartilage and are associated with Paget’s

disease, Ollier’s disease, and Maffucci’s syndrome. CT shows a well-defined lytic lesion with chondroid calcification. They are hyperintense on T2, hypointense on T1 with intense, often heterogenous enhancement. Most involve the clivus (32%) and tempo- ro-occipital junction (27%).

Unlike chordomas, chondrosarcomas typically occur off-midline due to their origin from sites of synchondrosis.

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Management is like that of chordomas. Treated chondrosarcomas have a good prognosis with 5-year mortality rate of 11.4%.9

13.2.3 Meningeal Tumors Meningiomas

These are the most common nonglial tumors which arise from arachnoid cap cells and account for 20 to 25% of all intracranial neoplasms. Most prevalent after age 50 with a F:M ratio of 2:1 and cranial:spine ratio of 10:1. Most (80%) are benign WHO grade I lesions that occur sporadically.

Multiple meningiomas occur in 1 to 9% of sporadic cases and as a feature of neurofibromatosis type 2 (NF2).

Risk factors include ionizing radiation, partial loss of chromosome 22 at the site involving the NF2 locus and protein 4.1B on 18p11.3. Progesterone receptors are present in half of meningiomas but this is of unknown significance. These may manifest as spherical, lobulated, or flat “en plaque” well-circumscribed dural lesions with clearly delineated tumor–brain interface. The majority appear hyperdense on CT with focal or diffuse calcification seen in 20 to 25%. Hyperostosis may be striking due to bony destruction. On MRI, they are T1 and T2 hypointense with homogeneous enhancement ( Fig. 13.3).

Surgery is the primary treatment modality. The Simpson Grading Scale10 ( Table 13.1) is used to describe the extent of resection and together with histological grade provides the most important prognostic indicator. Fractionated external beam or stereotactic radiosurgery is reserved for surgically inaccessible lesions, recurrence, and higher-grade lesions.

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Benign Mesenchymal Tumors

These are rare entities with variable clinical presentations, management, and prognosis. CNS rhabdomyomas are rare. Angiolipomas are associated with Proteus’ syndrome. These are composed of mature adipose tissue and abundant vascular channels of variable caliber without cytologic atypia or structural vascular channel abnormalities. Surgical resection may be curative. Chondromas are benign carti- lage-producing bony lesions that typically involve the long bones and appendicular skeleton. These present as sporadic lesions or as a component of Ollier’s disease or Maffucci’s syndrome. The lesions are difficult to distinguish from meningioma on neuroimaging and may have markedly delayed contrast enhancement. Surgical resection may be curative. Primary CNS leiomyomas (e.g., uterine fibroids) have rarely been described with fewer than 25 cases in the literature. They are associated with EBV infection in immunosuppressed patients. Lesions homogenously enhance and look like meningiomas. Gross total resection (GTR) is curative. Osteochondromas are benign tumors characterized by focal ossification within hyaline cartilage. They are usually sporadic but have been reported in the context of Maffucci’s syndrome, Noonan’s syndrome, and Ollier’s disease. There is avid contrast enhancement and are often confused with meningiomas.11 Benign fibrous histiocytoma is a rare mesenchymal lesion of soft tissue and bone with occasional retroperitoneal organ involvement. Dura and parenchyma are rarely involved. GTR may be curative but may behave more aggressively in older adults in whom it may be associated with recurrence and mortality. Adjunctive therapy should be considered in older individuals. Osteomas are benign bone-forming tumors usually involving the axial skeleton. These occur in the extremities of children