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

worse prognosis than Type I lesions.86 Due to their intramedullary location, high-flow malformations are usually treated endovascularly while asymptomatic patients can be followed conservatively.87

Fig. 10.3  Spinal dural arteriovenous fistula. (a) Sagittal T2-weighted image.

(b)Contrast-enhanced sagittal T1-weighted image.

(c)Sagittal high-resolution magnetic resonance angiography (MRA), maximum intensity projection (MIP) reconstruction.

(d)Coronal high-resolution

MRA, MIP reconstruction (slice 1). (e) Coronal high-­resolution MRA, MIP reconstruction­ (slice 2).

(f)Coronal high-resolution

MRA, MIP reconstruction (slice 3). (Reproduced from Forsting M, Jansen O, MR

Neuroimaging: Brain, Spine,

Peripheral Nerves, 1st edition, ©2016, Thieme Publishers, New York.)

spinal cord.92 These lesions may present with acute intraparenchymal hemorrhage, or with progressive neurological decline following multiple microhemorrhages.93

10.7.2 Cavernomas

Intramedullary spinal cavernomas account for 5–12% of all spinal vascular athologies.89,​ 90,​91 Only 3–5% of central nervous system (CNS) cavernomas are located in the

For cavernomas, the imaging modality of choice is MRI and it typical reveals a hyperintense T2 lesion (so called popcorn lesion), surrounded by a hypointense rim.

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Surgical resection is the primary treatment modality for symptomatic spinal cavernomas.94,​95,​96 However, conservative treatment is sometimes utilized in cases where a single bleed is followed by complete resolution of symptoms.

10.8  Spinal Deformity

The spine receives rotational and translational forces along its axial, coronal, and sagittal axes. According to this biomechanical paradigm, rotational forces are applied to the vertebrae when loads are carried eccentrically, causing shearing, compression, and distraction, and leading to degeneration and deformity in the sagittal, coronal, or axial planes.97 The normal spinal column consists of a cervical lordosis, a thoracic kyphosis, a lumbar lordosis and a sacral angulation, which must neutralize each other so that the head and trunk are located over the pelvis ensuring optimal load distribution and balance.

In clinical practice, standing 36-inch AP and lateral long films, with the hips and knees extended, are used to evaluate spinal deformity. Commonly used measurements include sagittal balance and the Cobb angle.

To determine sagittal spinal alignment on a lateral X-ray, a plumb line (line vertical to the floor) is dropped from the center of the C7 vertebra and should pass through

L1 and the posterior aspect of the L5/S1 disc space.

The Scoliosis Research Society has defined normal sagittal balance as the plumb line from C7 passing within 2 cm anterior or posterior to the sacral promontory (S1).98,​99 Deviation of the line more than 2 cm anteriorly is considered positive sagittal malalignment, while deviation

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more than 2 cm posteriorly is negative sagittal malalignment.

After determining sagittal balance, the lateral long X-ray should be used to evaluate angulation for each spine segment.

•The Cobb angle is the angle between intersecting lines drawn perpendicular to the top of the rostral vertebra and the bottom of the caudal vertebra (along the endplates) of the measured segment. Cervical lordosis has historically been accepted as normal at 40 ± 9.7°, thoracic kyphosis at 20–50° and lumbar lordosis at 31–79°.100,​101

This accounts for the commonly accepted

“40–50–60”ruleforcervical,thoracicand lumbar angulation respectively.

However, some studies have suggested this may overestimate the normal range.99

•Cobb angles are also used in the AP dimension to assess coronal balance ( Fig. 10.4). Normally, there should be 0° of angulation in any segment. If there is angulation, Cobb angles are used from the top of the rostral vertebra involved in scoliosis, to the bottom of the most caudal vertebra involved.102

•The apical vertebra is defined as the one with has the greatest rotation or furthest deviation from the midline.104

•The neutral vertebra is the first vertebra on an AP view where both pedicles are equally visualized, and shows no rotation.

•The stable vertebra is the first one to be bisected by the central sacral vertical line. Identification of these landmarks is critical to operative planning.103

The spinopelvic parameters are useful prognostic indicators for adult spinal deformity and include:

•Pelvic incidence (PI): Is the angle between a line drawn perpendicular to

the sacral plate (S1 endplate) at its midpoint and the line connecting this point to the femoral head axis.

•Pelvic tilt (PT): Is the angle between the line connecting the midpoint of the superior sacral plate to the axis of the femoral head and a vertical reference line.

•Sacral slope (SS): Is the angle between a horizontal line and the sacral

plate ( Fig. 10.5).104

•The PI-LL: Is the offset between pelvic incidence and lumbar lordosis.

•The sagittal vertical axis (SVA): Represents the linear offset of the C7 vertebra against the posterosuperior corner of S1. It is utilized to assess global sagittal alignment( Fig. 10.6).

The SVA, PT, and PI-LL have been most strongly associated with outcomes.104

There are three broad categories of spinal deformities—kyphosis, lordosis, and scoliosis, as well as combinations of these.

10.8.1 Kyphosis

Kyphosis is the pathological accentuation of the normal apical-dorsal sagittal contour of the thoracic and/or sacral spine. It may be combined with coronal abnormalities, in which case it is termed kyphoscoliosis. While there is wide variation in asymptomatic individuals, a Cobb angle less than 40° in the thoracic spine is generally considered normal.101 Kyphosis can lead to pain and cosmetic deformity with

severe cases developing neurological deficits and cardiopulmonary problems. Pain and functional disability is more common in adult kyphosis.81 Scheuermann disease is osteochondrosis of the spine in adolescents and is associated with pain and neurological symptoms in this group.105 It is characterized by 5° of wedging, at each level, over three consecutive vertebrae.106 Adult cases of kyphosis may arise following degenerative, inflammatory, traumatic, oncological, or infective disorders. Kyphosis follows a trimodal age distribution. Adolescents most commonly present with Scheuermann kyphosis, while patients in their 4th–6th decade present with associated ankylosing spondylitis (AS) or other inflammatory disorders, while elderly patients (> 60 years) present with degenerative changes.101 Diagnosis in the thoracic spine is made using 36-inch standing lateral radiographs with the hips and knees

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extended and with identification of a Cobb angle greater than 40°. Sagittal balance should be routinely assessed. An important consideration in management is assessing the flexibility of the spinal column. This is measured on a lateral radiograph of the patient lying supine over a bolster. Correction to 50° or less is considered flexible and can often be corrected with posteri- or-only fusion, while rigid deformities frequently require combined anterior and posterior procedures.107,​108

10.8.2 Lordosis

The most common pathological lordosis is lumbar hyperlordosis, which is prevalent in dancers, but can also be due to obesity, hyperkyphosis, discitis, Ehlers-Danlos Syndrome, or benign juvenile lordosis. It is associated with axial back pain and is usually managed with conservative treatment.109

10.8.3 Scoliosis

Scoliosis and kyphoscoliosis can occur in adolescent (adolescent idiopathic scoliosis) and adult (adult degenerative scoliosis) populations.110,​111 A rare form of scoliosis is

juvenile idiopathic scoliosis, which happens to children under the age of 10 years, who are skeletally immature. Scoliosis is classically defined as a Cobb angle greater than 10° in the coronal plane, although any angulation in the coronal plane can be

considered pathological.112 Scoliosis has two phases, curve initiation and progression.113 Bone growth in the immature spine is inhibited by pressure on the growth plate. The normally kyphotic thoracic spine places a greater axial load on the ventral aspect of the vertebral bodies. If there is rotation at any point, there will be differential pressure on the growth plate and the subsequent development of scoliosis.114 Reportedly, up to 95% of adolescent idiopathic scoliosis cases will progress and about 70% will require surgery.115 Management of scoliosis may involve observation, use of an orthosis, or surgery. Adolescent idiopathic scoliosis is categorized by curve type according to the Lenke classification system with lumbar spine and sagittal thoracic modifiers.116 Scoliosis with Cobb angles less than 20° are generally observed, those with 20–30° angles are treated with bracing and those with more than 30° angles may be surgically managed, taking into consideration bone maturity and the patient’s clinical state.117,​118,​119 Adult degenerative scoliosis progresses by approximately 3° per year.120 Surgery is recommended for coronal angulation of more than 45°.121

10.9  Inflammatory Spondyloarthropathies

10.9.1  Ankylosing Spondylitis

AS is an inflammatory disease of the joints of the spine and/or pelvis, and has a strong genetic component. It commonly presents with back pain and stiffness of the spine, which characteristically improves with exercise.122 Enthesitis and arthritis of other joints are common as are constitutional signs and fatigue.123 Moreover, AS is associated with extra-articular symptoms, including uveitis and cardiovascular disease.124 AS can be diagnosed with X-ray

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imaging of the spine and pelvis, with squaring and loss of the normal concave contour of the vertebral bodies and development of syndesmophytes (which can eventually produce a “bamboo spine” appearance and fusion of the sacroiliac joints).125 Inflammation at the points of joint insertion can cause sclerosis of the upper and lower limits of the vertebrae, characterized by the Romanus lesion. MRI and CT scans of the spine and pelvis may show early signs of sacroiliitis and enthesitis resulting in earlier diagnosis.126,​127 Medical treatment of AS consists of nonsteroidal anti-inflammatory drugs, sulfasalazine, corticosteroids, and tumor necrosis factor-α inhibitors. Spinal surgical man- agement can be considered in patients with complete fusion of a spine segment, but can be challenging, particularly in the context of traumatic injury, with associated anesthetic difficulties. These patients may benefit from osteotomy of the respective vertebral bodies.128,​129

10.9.2  Rheumatoid Arthritis of the Cervical Spine

Rheumatoid arthritis commonly presents in the cervical spine.130 The most common presenting pathologies are atlantoaxial subluxation, present in 49% of cases,131 superior migration of the odontoid in 38%, and subaxial subluxation in 10–20% of patients.132 About 25–80% of patients with rheumatoid arthritis will develop cervical spine involvement,133 with only a minority developing neurological symptomatology. Common presentations include facial pain, ear pain, occipital neuralgia, myelopathy, and vertebrobasilar insufficiency.

The clinical picture is classified according to the Ranawat classification134 as:

•Class I: Pain with no neurologic deficit.

•Class II: Subjective weakness, hyperreflexia, dysesthesias.

•Class III with objective problems, where:

◦Class IIIA: Objective weakness, long tract signs, ambulatory.

◦Class IIIb: Objective weakness, long tract signs, nonambulatory.

Operative treatment depends on the clinical symptomatology and imaging findings. Symptomatic pathologies may require intervention, while there is controversy as to whether patients with minimal symptoms but radiographic instability require surgery.135

10.10  Spinal Infections

10.10.1  Epidural Spinal Abscess

Abscesses in the spinal epidural space have a reported incidence of 2.8 cases per 100,000 admissions and this figure is rising in the intravenous drug abusing population.136

The most common pathogen identified is Staphylococcus aureus.137

The abscess can lead to pain and neurological deficits through local mass effect and compression of the spinal cord/nerve roots as well as vascular compromise of the spinal cord leading to subsequent spinal cord ischemia. Symptomatology may evolve in four stages:138,​139

1.Axial back pain at the affected spinal level.

2.Radicular pain at the affected nerve root.

3.Motor and sensory abnormalities, bladder and bowel dysfunction.

4.Paralysis.

The classic triad of spinal epidural abscess includes fever, back pain, and neurological deficit.137 Suspicion for epidural abscess

should prompt immediate spinal MRI (ideally with contrast) to identify the lesion. Both medical and surgical management can be considered for these patients, as there is controversy regarding the optimal management strategy.140,​141 As a general rule, if neurological status is impaired or if the spine is unstable, then surgery is indicated. For patients with pain only and no neurological or stability issues, then empiric antibiotic therapy with antistaphylococcal coverage may be administered as part of a conservative treatment regimen, which can be tailored as cultures identify specific organisms. Stable patients without neurological deficits may undergo CT-as- sisted abscess aspiration, but any deterioration in clinical status should prompt emergency spinal decompression to avoid permanent neurologic deficit.

10.10.2  Vertebral Body Osteomyelitis

Vertebral body osteomyelitis (VBO) is the most common form of infection of the vertebral column. Pyogenic vertebral osteomyelitis was found primarily in older individuals with comorbidities such as diabetes mellitus, alcoholism, renal or liver failure, cancer, or immunosuppression, and younger intravenous drug abusers.142 Symptomatology may be nonspecific, with an absence of fever in 40% of cases.142 The most common bacterial species isolated is Staphylococcus aureus, followed by Escherichia coli.142 CT scanning is valuable to evaluate bony erosion,143 while MRI can assist in earlier detection of osteomyelitis and abscesses. Uncomplicated VBO should be initially treated with intravenous antibiotics for 4–6 weeks, and this may be followed by oral antibiotics for a further 2–6 weeks.144 Immobilization with bedrest and/or use of an external orthosis may be considered as well. Surgical management may be needed for biopsy, symptomatic spinal cord compression, or refractory severe pain.

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Follow-up imaging has not been shown to correlate with better results, so patients should be followed clinically to ensure response to antibiotics.142

10.10.3  Pott’s Disease

Tuberculosis of the spinal column, also known as Pott’s disease, involves both osteomyelitis and arthritis. In adults, tuberculosis spreads from the anterior aspect of the vertebra. In children, osteomyelitis most commonly spreads hematogenously, primarily affecting the intervertebral discs. A predilection for destruction of the anterior parts of the vertebral bodies can lead to kyphosis in addition to abscess formation and direct compression of the spinal cord. Patients with suspected Pott’s disease should be assessed with a tuberculin (purified protein derivative) test and percutaneous CT-guided biopsy for culture.146 The gold standard for the evaluation of Pott’s disease is MRI, which shows characteristic thin and smooth enhancement of the abscess wall and a well-defined paraspinal signal.146 Antituberculous medications are indicated in these patients, and surgery can be indicated in patients with neurological deficits or instability.147

10.11  Cauda Equina Syndrome

In most adults, the spinal cord will taper and end caudally at approximately the L1 level, forming the cauda equina, a collection of nerve roots that looks like a “horse’s tail”.

Although the cauda equina is part of the peripheral nervous system, its compression may cause irreversible neurologic deficits and is, therefore, an emergency.148 The cauda equina nerve roots may be particularly vulnerable due to their thin myelin sheath.149 Common causes of cauda equina syndrome are traumatic,150 degenerative,151

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and malignant.152 Degenerative lumbar disc disease can lead to cauda equina syndrome, with 70% of patients having back pain prior to the onset of cauda equina symptoms.153 Neoplasms are an uncommon causes of cauda equina syndrome. However, the most common neoplastic pathological diagnoses are myxopapillary ependymomas,154 schwannomas,155 and paragangliomas.156 The symptoms in cauda equina syndrome are:

•LBP.

•Radiculopathy (more commonly unilateral).

•Saddle anesthesia.

•Bowel/bladderretention. incontinence or

•Bilateral lower extremity motor and sensory deficit.

•Absent lower extremity reflexes.

Suspicion for cauda equina syndrome should be raised in patients with acute LBP accompanied by urinary changes. The diagnostic study of choice is MRI of the lumbosacral spine.157 Surgical decompression is undertaken as an emergency in the first 48 hours, and preferably within in the first 6 hours of the onset of cauda equina syndrome.158 Laminectomy with neural decompression is essential and in cases where stability is compromised, a fusion may be added. In addition, tumor resection may be attempted in emergency cases where a neoplasm is the underlying pathology.

10.12  Other Spinal Syndromes

10.12.1  Failed Back Surgery Syndrome

Failed Back Surgery Syndrome (FBSS) is defined as persistent or recurrent back pain after one or more surgeries that failed to improve the clinical condition.159 It may be caused by residual or recurrent disc

herniation, alteration of spinal biomechanics and mobility, scar tissue, or psychological disturbances. Management modalities for FBSS include:160

•Physical therapy.

•Chiropractic care.

•Nonsteroidal anti-inflammatory drugs.

•Transcutaneous electrical stimulation (TENS).

•Facet joint injections.

•Antidepressants.

•Spinal cord stimulation (SCS).

•Intrathecal drug pump (IDP).

As both SCS and IMP are implantable devices used as a last resort in FBSS, a trial is offered before permanent implantation with these procedures. SCS is preceded by percutaneous implantation of an electrode to assess diagnostic and therapeutic responses, while IDP trials consist of a single intrathecal injection of morphine. The decision of one modality over the other is based on patient and physician preferences.

10.12.2  Tethered Cord Syndrome

Tethered cord syndrome is associated with thickening of the filum terminale causing tethering of the conus medullaris to the dorsal aspect of the spinal canal. It is associated with myelomeningoceles, scoliosis, and VACTERL (vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal anomalies, and limb abnormalities) syndrome.161 Symptoms include deformities in the lower extremities and the spine, and peripheral stigmata, such as lower back lesions (hairy patch, dimples etc.) may be present. Lower extremity motor or gait disturbances, bladder disorders, LBP, and scoliosis can also accompany tethered cord syndrome. The diagnosis can be made with MRI. However, often times, clinical judgement is needed to ultimately decide which patients would benefit from

surgical intervention.162 Early operative treatment is necessary in symptomatic patients to prevent neurological deterioration and permanent damage.163 Surgery most often involves untethering the cord from the vertebrae; occasionally, a spine-shortening vertebral osteotomy may be performed.164

Pearls

•A thorough history and physical examination can be used to discern between the different etiologies of LBP including fracture-dislocations, spinal neoplasms, and infections.

•The most common spinal tumors are vertebral body metastases and the SINS score is a validated tool that should be used to evaluate these lesions.

•Spinal deformity should be assessed on standing 36-inch AP and lateral long films by calculating the sagittal balance and Cobb angle.

•Acute low back pain accompanied by lower extremity weakness and bowel/bladder symptoms should raise suspicion for cauda equina syndrome, which is a surgical emergency.

10.13  Top Hits

10.13.1  Questions

1.The spinopelvic parameter defined as the angle between the perpendicular to the sacral plate at its midpoint and the line connecting this point to the femoral head axis, is:

a)Pelvic incidence

b)Pelvic tilt

c)Sacral slope

d)Sagittal vertical axis

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2.The most commonly isolated bacterial species in patients with vertebral body osteomyelitis is:

a)Escherichia coli

b)Staphylococcus aureus

c)Pseudomonas aeruginosa

d)Streptococcus equisimilis

3.According to the classification system developed by Anson and Spetzler, “low flow” spinal vascular malformations are defined as:

a)Type 1 (dural AVFs)

b)Type 2 (glomus AVMs)

c)Type 3 (juvenile intramedullary and extramedullary AVMs)

d)Type 4 (pial AVFs)

10.13.2  Answers

1.a. The pelvic incidence is defined as the angle between the perpendicular to the sacral plate at its midpoint and the line connecting this point to the femoral head axis.

2.b. The most common bacterial species isolated in patients with vertebral osteomyelitis is Staphylococcus aureus.

3.a. Type 1 (dural AVFs) spinal vascular malformations are defined as “low flow” lesions. Types 2, 3, and 4 are “high flow” lesions.

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