George Georgoulis

Ventilator waveforms on anesthesia machine: A simple tool for intraoperative mapping of phrenic nerve and mid-cervical roots

BackgroundA crucial aspect of surgery on the supraclavicular region, lateral neck, and mid-cervical vertebral region is the identification and sparing of the phrenic nerve and cervical (C4) root that are responsible for diaphragmatic innervation. Therefore intraoperative mapping of these nerve structures can be useful for difficult cases. Electrical stimulation with simultaneous observation of the ventilator waveforms of the anesthesia machine provides an effective method for the precise intraoperative mapping of these structures. In the literature, there is only one publication reporting the use of one of the waveforms (capnography) for this purpose.MethodsCapnography and pressure–time waveforms, two mandatory curves in anesthesiological monitoring, were studied under electrical stimulation of the phrenic nerve (one patient) and the C4 root (eight patients). The aim was to detect changes that would verify diaphragmatic contraction. No modifications in anesthesia or surgery and no additional maneuvers were required.ResultsIn all patients, stimulation was followed by identifiable changes in the two waveforms, compatible with diaphragmatic contraction: acute reduction in amplitude on capnography and repetitive saw-like elevations on pressure–time curve. Frequency of patterns on pressure–time curve coincided with the frequency of stimulation; therefore the two recordings were complementary.ConclusionsThis simple method proved effective in identifying the neural structures responsible for diaphragmatic function. We therefore suggest that it should be employed in the various types of surgery where these structures are at risk.

Surgery in Dorsal Root Entry Zone

Surgery in the dorsal root entry zone (DREZ) was introduced in 1972 to treat some types of topographically limited pain. Because of its inhibitory side-effects on muscular tone, namely, the induction of marked hypotonia, the method was applied to patients with severe focalized hyperspasticity. The technique was termed microsurgical DREZotomy (MDT) because it is performed by microsurgical techniques and with the bipolar coagulation microforceps as the lesion maker. The method attempts to selectively interrupt the small myelinated fibers (considered nociceptive) and the large myelinated myotatic fibers situated laterally and centrally, respectively, whilst partly sparing the large myelinated (considered sensory primary afferent) fibers located medially to reach and ascend through the dorsal columns. Surgery in the DREZ requires strong knowledge of spinal cord anatomy.

Intrathecal Baclofen Therapy

Baclofen, a γ-aminobutyric acid-B (GABA-B) receptor agonist, has a direct action on the receptors of the dorsal horn gray matter, where density of GABA-B receptors is high. Baclofen activates GABA-B presynaptic receptors that inhibit the release of excitatory neurotransmitters of the dorsal horn, particularly aspartate and glutamate. The excitability of monosynaptic and polysynaptic reflexes of the spinal cord becomes thereby reduced. Given orally, baclofen has a weak capacity to penetrate the blood–central nervous system barrier. After oral administration the drug is absorbed by more than 80 % through the intestinal mucosa the plasmatic concentration is maximal within 90–120 min; most is eliminated by urinary excretion. Failure of oral medication to produce sufficient reduction of spasticity is due to the poor passage of the drug across the blood–central nervous system barrier. In animal experiments, the concentration in the cerebrospinal fluid (CSF) was less than one-tenth of that in the plasma level. Systemic delivery would produce the same concentrations along the spinal cord and would be distributed equally to the brain, and the consequences would be somnolence or even coma. To circumvent this problem, Penn and Kroin introduced and developed the method of delivering baclofen intrathecally by subarachnoid lumbar infusion.

History of Neurosurgical Treatment for Spasticity

The history of neurosurgery for spasticity is strongly linked to the beginning of neurosurgery. With the discovery of the stretch reflex by Sherrington and the quality of the clinical studies at that time, especially the description of the different kinds of hypertonia by Babinski, the new surgeons of the nervous system started early with interruption procedures on dorsal roots (Foerster) or peripheral nerves (Lorenz, Stoffel). In France, this field of functional neurosurgery grew rapidly. Gros in Montpellier improved the technique of dorsal rhizotomy, while Sindou in Lyons, created the technique of drezotomy after studies on pain mechanisms. The history was then followed in Chicago by Penn and Kroin who developed the technique of intrathecal baclofen which indications are still increasing today. Improvement of knowledge on neurophysiology and control of movement lead to an optimisation of the surgical procedures where French speaking neurosurgery plays an important role.

Focal Dystonia in Hemiplegic Upper Limb: Favorable Effect of Cervical Microsurgical DREZotomy Involving the Ventral Horn - A Report of 3 Patients

Background: Focal dystonia in hemiplegic upper limbs is poorly responsive to medications or classical neurosurgical treatments. Only repeated botulinum toxin injections show efficacy, but in most severe cases effects are transient. Objectives: Cervical DREZ lesioning, which has proven efficacious in hyperspasticity when done deeply (3-5 mm) in the dorsal horn, may have favorable effects on the dystonic component when performed down to, and including, the base of the ventral horn (5-6 mm in depth). Methods: Three patients underwent deep cervical microsurgical DREZotomy (MDT) for focal dystonia in the upper limb. Results: Hypertonia was reduced, and sustained dystonic postures were suppressed. Residual motor function (hidden behind hypertonia) came to the surface. Conclusions: Cervical MDT may be a useful armamentarium for treating refractory focal dystonia in the upper limb.

Anatomical and Physiological Bases of Motricity Applied to the Study of Spasticity

The spinal motoneuron is under permanent influence of peripheral afferent fibers, interneurons, and descending projections from supraspinal structures. Spasticity corresponds to the exaggeration of the monosynaptic reflex (Fig. 3.1). Various lesions of the central nervous system give rise to spasticity, especially if they affect the supraspinal descending controls, mainly the reticulospinal tracts.

Spasticity in Cerebral Palsy

The most frequent cause of spasticity and hypertonia in childhood is by far cerebral palsy (CP). In 1861 Little was the first to draw the medical community’s attention “on the influence of abnormal parturition, difficult labours, premature birth, and asphyxia neonatorum, on the mental and physical condition of the child, especially in relation to deformities”. The term “cerebral palsies of children” was established in 1889 by Osler. The presently adopted description of CP was given by Ingram. CP is now worldwide used to designate nonprogressive disorders of the motor and related functions that result from an insult to the brain which occurs in the prenatal, perinatal, or approximately 2-year postnatal period, or due to excessive prematurity. There are different clinical patterns of hypertonia within the frame of CP disorders.

Decision-Making for Treatment of Adults with Disabling Spasticity

Spasticity should not be treated just because it is present; it should be treated when it is harmful. Indeed, paralyzed patients may make use of spasticity for functional activities. An extensor pattern in the lower limb(s) allows the hemiplegic patient to walk and helps the paraplegic patient in standing transfers. In these scenarios, a “successful” treatment of the spasticity, as measured by reduction in tone and improved range of motion, could well reduce rather than enhance function [1]. Differentiation of reversible abnormal postures from fixed deformities is of prime importance before indicating surgical treatment. Operative methods for a reduction of spasticity can be classified according to their effects being either focal or general and being either permanent or temporary

Dorsal Rhizotomies for Children with Cerebral Palsy

Since the late nineteenth century, dorsal rhizotomies (DR) have been known to alleviate spasticity. But only in the last 20 years, DR became commonly used after refinements in surgical indications and selection of roots and rootlets on their topographic and/or functional responses to stimulation.

Management of Hyperactive Bladder

Overactive bladder, with its complications on the upper urinary tract, is a frequent occurrence after damage of the central nervous system, especially at the spinal cord level.