Anaesthesia for spinal surgery in adults D.A. Raw, J.K. Beattie, J.M. Hunter  British Journal of Anaesthesia  Volume 91, Issue 6, Pages 886-904 (December 2003) DOI: 10.1093/bja/aeg253 Copyright © 2003 British Journal of Anaesthesia Terms and Conditions

Fig 1 (a) Thoracolumbar scoliosis and measurement of the Cobb angle. A perpendicular line is drawn from the end plate of the most caudal vertebrae involved, whose inferior end plate tilts maximally to the concavity of the curve. A second perpendicular line is drawn from the end plate of the most cephalad vertebrae, whose superior end plate tilts maximally to the concavity of the curve. The curve value is the number of degrees formed by the angle of intersection of these two lines. (b) Thoracolumbar scoliosis after surgery, showing long rods and pedicle screws. (c) Dislocation of the 5th and 6th cervical vertebrae after trauma; (d) same patient’s MRI scan, and (e) after surgery to stabilize the cervical spine. SC, spinal cord; C6, sixth cervical vertebrae. British Journal of Anaesthesia 2003 91, 886-904DOI: (10.1093/bja/aeg253) Copyright © 2003 British Journal of Anaesthesia Terms and Conditions

Fig 2 Algorithm for decision making when intubating a patient for proposed surgery involving the upper thoracic or cervical spine. ILMA, intubating laryngeal mask airway; FO, fibre-optic; RSI, rapid sequence induction; NDNMB, non-depolarizing neuromuscular blocking agent. British Journal of Anaesthesia 2003 91, 886-904DOI: (10.1093/bja/aeg253) Copyright © 2003 British Journal of Anaesthesia Terms and Conditions

Fig 3 Diagrammatic representation of motor and sensory pathways of the spinal cord. The lateral and anterior corticospinal tracts subserve voluntary movement. The upper motor neurone axon, with its cell body in the primary motor cortex, descends via the internal capsule to the medulla oblongata. Most motor fibres (85%) cross the midline at the pyramidal decussation to descend the contralateral spinal cord as the lateral corticospinal tract. The remainder (15%) do not cross the midline and descend the ipsilateral spinal cord as the anterior spinal tract. The corticospinal tracts must be functionally intact in order for MEP to be recorded, and the Stagnara wake-up test to be performed. The dorsomedial sensory tracts subserve discriminatory touch, proprioception, and vibration senses. The primary sensory neurone, with its cell body in the dorsal root ganglion of the spinal cord, sends fibres in the dorsal aspect of the ipsilateral spinal cord to the medulla oblongata where they synapse. The second order sensory neurone projects fibres to the thalamus after crossing the midline. After synapsing with the tertiary sensory neurone in the thalamus, fibres are projected to the primary somatosensory cortex. This pathway must be functionally intact in order for SSEPs to be recorded. British Journal of Anaesthesia 2003 91, 886-904DOI: (10.1093/bja/aeg253) Copyright © 2003 British Journal of Anaesthesia Terms and Conditions

Fig 4 Diagrammatic representation of typical recordings of somatosensory and MEP. (a) Cortical SSEP recordings after stimulation of the tibial nerve at the ankle. In accordance with international convention, positive waves are represented by downward deflections and labelled P1, P2, etc. Negative waves are represented by upward deflections, labelled N1, N2, etc. (b) Cortical MEP recordings. After magnetic stimulation of the motor cortex, compound muscle action potentials are recorded from electrodes placed in biceps brachii under partial neuromuscular block. British Journal of Anaesthesia 2003 91, 886-904DOI: (10.1093/bja/aeg253) Copyright © 2003 British Journal of Anaesthesia Terms and Conditions

Fig 5 Diagrammatic representation of a transverse section through the spinal cord at the level of the sixth thoracic vertebra. Motor fibres subserving voluntary movement descend the spinal cord as the lateral (crossed) and anterior (uncrossed) corticospinal tracts. Sensory fibres subserving discriminatory touch, proprioception and vibration sense ascend the spinal cord as the fasciculus gracilis and fasciculus cuneatus, which together are termed the dorsomedial columns. The f. gracilis conveys sensory fibres, which originate from sacral, lumbar and lower thoracic levels. The f. cuneatus conveys sensory fibres, which originate from upper thoracic and cervical levels of the spinal cord. The blood supply of the spinal cord is from the anterior spinal artery (formed by the union of a branch from each vertebral artery), which supplies the anterior two-thirds of the spinal cord including the corticospinal tracts (unshaded area), and from the posterior spinal arteries (derived from the posterior cerebellar arteries) which supply the posterior third of the cord including the dorsomedial columns (shaded area). These arteries are reinforced by a variable number of medullary feeding vessels from the vertebral arteries in the cervical area, and vessels (including the Artery of Adamkiewicz) from the aorta in the thoracic and lumbar areas. British Journal of Anaesthesia 2003 91, 886-904DOI: (10.1093/bja/aeg253) Copyright © 2003 British Journal of Anaesthesia Terms and Conditions