Legacy: "Atlast of Neurosurgery" / L.Karaguiosov, A. Ramadan, K.Karaguiosov / Kiwait/ 1998
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17. INFECTIONS OF THE SPINE AND SPINAL CORD
Infections of the spine and spinal cord that need surgical treatment are rare compared to the frequency of cranial and intracranial infections. According to the aetiology they are of different categories: granulomatous, pyogenic, parasitic. Tuberculosis is very rare in developed countries. In many other countries tuberculous spondylitis with affection of the spinal cord is still a serious problem and on many occasions needs surgical treatment. Pyogenic haematogenous osteomyelitis, spinal epidural abscess and infections of the intervertebral discs on many occasions need surgical treatment. Subdural and intramedullary abscesses are very rare, and surgical treatment is essential to avoid permanent damage of the spinal cord and nerve roots. Parasitic infections in endemic areas are common. In the present era of migrating populations, it is possible to find a parasitic disease such as hydatid cyst or cysticercosis in a patient with a suspected spinal tumour.
TUBERCULOUS SPONDYLIS
Active tuberculous spondylitis causes a neurological deficit by pressure and toxic effects from pus, granulation tissue, bony sequestration, intervertebral disc material and bony dislocation. Direct penetration of the dura is rare; where it does occur, it causes tuberculous meningitis or meningomyelitis.
Healed disease also causes a neurological deficit by the remaining internal bony ridge or fibrous tissue constriction of the spinal cord.
Clinical presentations include signs and symptoms of infection: fever, malaise and weight loss. Evidence of tuberculous involvement in other organs may be present. Other manifestations include localised spinal pain in the early stage, followed by spinal deformity later. Muscle spasm is common with limited spinal movement. Back pain is present and aggravated by movement. With presence of a kyphotic deformity, adjacent segments in the spine develop compensatory lordosis.
Neurological manifestations develop slowly and progressively, but occasionally they can start suddenly. Neurological deficit is expressed to a varying degree. as ambulation may be difficult, and in advanced cases complete paraplegia or quadriplegia is present.
Diagnostic X-rays can demonstrate destruction, paravertebral abscesses, and deformities of the spine. Myelographic studies confirm spinal cord compression. A CT scan will define the extent of the paraspinal abscess and calcifications, together with the bone destruction. MRI provides additional data on the pathological changes within the spine and the spinal canal (Fig. 17-1). The definitive diagnosis is based on a combination of clinicoradiological features, and in particular positive histology of specimens obtained at operation.
SURGICAL MANAGEMENT
A complete course of antituberculous chemotherapy still remains the basis of treatment for all forms of active spinal tuberculosis. In cases with a neurological deficit, especially if it is progressing, surgical treatment is required. Operation essentially consists of excision of the disease focus and grafting. Abscess and granulation tissue evacuation will very often rapidly alleviate pain and improve the clinical condition of the patient. Alleviation of pressure on neural structures will enhance early neurological recovery, this being an absolute indication for surgery. The thorough debridement and placement of a bone graft under axial compression will enhance early fusion. The increasing deformity is prevented with early fusion, and late spinal cord compression from a bony bar is also prevented.
The operation consists of two main elements: 1. Eradication of the tuberculous focus by removing pus, sequestration of disc, bony fragments, and granulation tissue until the normal bone tissue is reached. 2. A slightly oversized graft is put under compression in an attempt to open the kyphosis during its insertion (Figs. 17-2; 17-3). As bone grafts, either a rib removed during thoracotomy, or the iliac crest are used. After placing the first bony piece, the rest of the bony defect is packed firmly with additional pieces. The next stage of the operation is posterior spinal fusion if anterior grafts are to replace two or more vertebral bodies. In cases of neurological deficit in patients with healed disease, the offending anterior bone ridge and fibrosis compressing the spinal cord should be removed.
As the destruction focus usually is situated in the vertebral bodies, the surgical approach should be anterior or anterolateral. The C1 and C2 vertebra are approached, usually transorally (Fig. 17-4). Infection in the oropharyngeal cavity should be treated before surgery. Tracheostomy is usually necessary for the anaesthesia.
The neck is extended and a special retractor maintains the mouth open with the tongue depressed. The soft palate is incised in the midline and the incision passes in one side of the base of the uvula. The two pieces of the soft palate are retracted by traction threads. After packing the hypopharynx, the anterior tubercle of the atlas is palpated and an anterior midline incision of the posterior pharyngeal wall is made. The two borders of the incised pharyngeal wall are retracted and stay-sutured. The prevertebral fascia and the fibrous tissue anterior to the vertebra are incised and the anterior surface of the vertebrae is reached and stripped.
The prevertebral abscess if present is removed. Granulation tissue inside the cavity and necrotic bone are curettaged. A slot is created for an inlay graft in the midline. If C1 - C2 dislocation is present gentle hyperextension of the head often reduces the displacement.
The C3 - C7 vertebrae are approached by penetrating between the neurovascular bundle in the neck laterally and the pharynx, larynx and trachea medially. A transverse skin incision in a small tuberculous focus along the skin creases is preferable from the cosmetic point of view. A vertical incision along the sternomastoid muscle may be necessary, if an extensive exposure over multiple levels is needed. The superficial cervical fascia is divided and the omohyoid muscle is identified and retracted or divided. The carotid sheath is retracted laterally and the larynx, pharynx, trachea and oesophagus - medially. The prevertebral fascia is incised vertically in the midline, taking care not to damage the sympathetic trunks. The tuberculous focus is approached between the deep prevertebral muscles (Figs. 17-5; 17-6).
The approach of the cervico-thoracic junction is a difficult one. When a single vertebra is in-volved, access can be either through the neck or the chest. With multiple vertebrae involvement together with significant kyphosis, a split sternum approach can be applied. An alternative is to excise or elevate one half of the manubrium, the sternoclavicular joint and the medial half of the clavicle on a pedicle of sternocleidomastoid muscle.
The thoracic vertebral bodies can be approached through a costotransversectomy or thoracotomy for lesions from T2 to TI2.
In costotransversectomy, the cutaneous incision takes the form of an arch, beginning from the midline 10 cm above the affected vertebra, and at the same level 10 cm laterally from the mid-line, ending on the midline again 10 cm below the vertebral pathology. The convexity of the arch is on the side of the more expressed neurological deficit. A flap is formed from the skin and the subcutaneous tissue and fascia, and turned medially. The superficial paravertebral muscles are cut perpendicularly to the midline, and are separated from the rib, which will be resected. The paravertebral muscles are dissected and separated upward and downward. In this way the transverse processes of 3 - 4 vertebrae together with the medial parts of the respective ribs are exposed. The rib corresponding to the level of the tuberculous focus is stripped from the periosteum and is resected from 6 to 8 cm. After that the transverse process and the head of the rib are resected too, and the lateral aspect of the vertebra is reached. These manipulations have to be done carefully, in order not to open the pleural cavity (Figs. 17-7; 17-8).
A thoracotomy approach, usually on the right side for a lesion from C7 to T4 and the left side for a lesion from T4 to T12, is preferred. On the left side, the aorta is a useful landmark and is less liable to be damaged as compared to the vena cava on the right side. The patient is in a lateral position on the operative table, usually with a sandbag or the bridge of the table under the involved vertebrae. The rib to be excised is usually two levels or higher than the centre of the tuberculous focus. After excising the rib subperiosteally the parietal pleura is incised throughout its exposed length. After retraction of the lung forward, the space between the great vessels (aorta and vena cava) is seen. If there is no abscess, the great vessels are mobilised from the vertebral body after incising the parietal pleura.
The approach the thoracolumbar junction: a left thoracotomy is used, with removal of the ninth rib. The pleural cavity is entered and the aorta mobilised. The retroperitoneal space is entered, usually at the costal cartilage of the ninth rib. The parietal peritoneum is mobilised from the undersurface of the diaphragm and retracted antero-inferiorly. The diaphragm is then cut circumferentially, leaving a 1 cm edge so that approximation is possible during wound closure. Approaching the vertebral bodies, the psoas muscle must be mobilised from the vertebral bodies.
To approach the lumbosacral spine (L2 - S1) is preferred the left side because the major arterial vessels are easier to deal with than are the venous vessels. A lateral position of the patient is used on the operative table. An oblique incision is made posteriorly, starting at the midpoint between the iliac crest and the costal margin and extending to the midpoint between the umbilicus and the anterior superior iliac spine. After cutting the abdominal muscles, the retroperitoneal space is entered by stripping the parietal peritoneum from the posterior and lateral abdominal wall; the ureter, and kidney are reflected medially with the rest of the abdominal content. In approaching the lumbosacral junction, the common and external iliac vessels are mobilised. The iliolumbar artery must be identified and sometimes ligated. If damaged or cut, the sympathetic chain does not provoke any permanent deterioration. The psoas muscle is mobilised and its origin detached.
Postoperative management. Immobilisation is necessary for at least the initial three months.
A collar or halo-jacket type immobilisation is needed for the cervical spine, depending on stability and length of the graft.
Complications. During the operation, vascular, visceral or neural damages may occur.
Minor vascular tears can be repaired or the vessel can be ligated if it is appropriate. A major vascular accident may occur if the anatomy is grossly distorted and marked fibrosis makes the dissection difficult. A vascular surgeon's assistance may be necessary if such a major complication occurs. The lung and ureter are the structures vulnerable during the surgery. After freeing the lung from adhesions, if there is proper air filling, insertion of a chest drain is sufficient. Any damage of the ureter must be repaired to prevent leakage or a postoperative fistula. Dural tears require closure; otherwise a fistula and/or cerebrospinal fluid accumulation will occur. The lumbar plexus overlying a fibrotic psoas muscle may also be damaged during the removal of an abscess or mobilisation of the muscle.
Post-thoracotomy complications include pleural effusion, haemothorax, lung collapse and pneumonia. These can be prevented by good postoperative care and chest physiotherapy. Retroperitoneal dissection in the dorsolumbar and lumbar region often results in transient paralytic ileus.
Minor postoperative neurological complications include transient Horner's syndrome due to cervical sympathetic damage. The appearance of postoperative deterioration of the spinal cord function (paraparesis or tetraparesis) is due to either spinal cord damage or spinal cord compression by slippage of a bone graft.
