Jozef Maršala

Cauda equina syndrome

Single or double-level compression of the lumbosacral nerve roots located in the dural sac results in a polyradicular symptomatology clinically diagnosed as cauda equina syndrome. The cauda equina nerve roots provide the sensory and motor innervation of most of the lower extremities, the pelvic floor and the sphincters. Therefore, in a fully developed cauda equina syndrome, multiple signs of sensory disorders may appear. These disorders include low-back pain, saddle anesthesia, bilateral sciatica, then motor weakness of the lower extremities or chronic paraplegia and, bladder dysfunction. Multiple etiologies can cause the cauda equina syndrome. Among them, non-neoplastic compressive etiologies such as herniated lumbosacral discs and spinal stenosis and spinal neoplasms play a significant role in the development of the cauda equina syndrome. Non-compressive etiologies of the cauda equina syndrome include ischemic insults, inflammatory conditions, spinal arachnoiditis and other infectious etiologies. The use of canine, porcine and rat models mimicking the cauda equina syndrome enabled discovery of the effects of the compression on nerve root neural and vascular anatomy, the impairment of impulse propagation and the changes of the neurotransmitters in the spinal cord after compression of cauda equina. The involvement of intrinsic spinal cord neurons in the compression-induced cauda equina syndrome includes anterograde, retrograde and transneuronal degeneration in the lumbosacral segments. Prominent changes of NADPH diaphorase exhibiting, Fos-like immunoreactive and heat shock protein HSP72 were detected in the lumbosacral segments in a short-and long-lasting compression of the cauda equina in the dog. Developments in the diagnosis and treatment of patients with back pain, sciatica and with a herniated lumbar disc are mentioned, including many treatment options available.

Neuropathic pain is associated with alterations of nitric oxide synthase immunoreactivity and catalytic activity in dorsal root ganglia and spinal dorsal horn

Previous experiments have suggested that nitric oxide may play an important role in nociceptive transmission in the spinal cord. To assess the possible roles of neuronal nitric oxide synthase (nNOS) in spinal sensitization after nerve injury, we examined the distribution of nNOS immunoreactivity in dorsal root ganglia (DRGs) and dorsal horn of the corresponding spinal segments. NOS catalytic activity was also determined by monitoring the conversion of [3H]arginine to [3H]citrulline in the lumbar (L4-L6) spinal cord segments and DRGs in rats 21 days after unilateral loose ligation of the sciatic nerve. Behavioral signs of tactile and cold allodynia developed in the nerve-ligated rats within 1 week after surgery and lasted up to 21 days. Immunocytochemical staining revealed a significant increase (approximately 6.7-fold) of nNOS-immunoreactive neurons and fibers in the DRGs L4-L6. No significant changes were detected in the number of nNOS-positive neurons in laminae I-II of the spinal segments L4-L6 ipsilateral to nerve ligation. However, an increased number of large stellate or elongated somata in deep laminae III-V of the L5 segment expressed high nNOS immunoreactivity. The alterations of NOS catalytic activity in the spinal segments L4-L6 and corresponding DRGs closely correlated with nNOS distribution detected by immunocytochemistry. No such changes were detected in the contralateral DRGs or spinal cord of sham-operated rats. The results indicate that marked alterations of nNOS in the DRG cells and in the spinal cord may contribute to spinal sensory processing as well as to the development of neuronal plasticity phenomena in the dorsal horn.

Spinal Cord Gray Matter Layers Rich in NADPH Diaphorase-Positive Neurons Are Refractory to Ischemia–Reperfusion-Induced Injury: A Histochemical and Silver Impregnation Study in Rabbit☆

Silver impregnation analysis of neuronal damage and concurrent histochemical characterization of NADPH diaphorase-positive neuronal pools in the rabbit lumbosacral segments was performed during and after transient spinal cord ischemia. Strongly enhanced staining of NADPH diaphorase-positive neurons and their processes appeared in the superficial dorsal horn (laminae I-III), the pericentral region (lamina X) of lower lumbar segments, the lateral collateral pathway, and mainly in neurons of the sacral parasympathetic nucleus in the S2 segment at the end of 40 min of abdominal aorta ligation or 1 day after reperfusion. Despite the development of extensive neuronal degeneration in the central gray matter (laminae IV-VII) between 1 and 4 days after ischemia, a number of nonnecrotizing neurons localized in the areas corresponding with the distribution of NADPH diaphorase-positive neurons was detected, suggesting a selective resistance of these classes of neurons against transient ischemic insult. While the precise mechanism of the observed resistance is not known, it is postulated that region-specific synthesis of nitric oxide and its vasodilatatory effect during the period of incomplete spinal ischemia may account for the observed selective resistance of these spinal cord neurons to transient ischemia.

Development of GABA-sensitive spasticity and rigidity in rats after transient spinal cord ischemia: a qualitative and quantitative electrophysiological and histopathological study.

Transient spinal cord ischemia may lead to a progressive degeneration of spinal interneurons and subsequently to increased hind limb motor tone. In the present work we sought to characterize the rigidity and spasticity components of this altered motor function by: i) tonic electromyographic activity measured in gastrocnemius muscle before and after ischemia, ii) measurement of muscle resistance during the period of ankle flexion and corresponding changes in electromyographic activity, iii) changes in Hoffmann reflex, and, iv) motor evoked potentials. In addition the effect of intrathecal treatment with baclofen (GABAB receptor agonist; 1 microg), nipecotic acid (GABA uptake inhibitor; 300 microg) and dorsal L2-L5 rhizotomy on spasticity and rigidity was studied. Finally, the changes in spinal choline acetyltransferase (ChAT) and vesicular glutamate transporter 2 and 1 (VGLUT2 and VGLUT1) expression were characterized using immunofluorescence and confocal microscopy. At 3-7 days after ischemia an increase in tonic electromyographic activity with a variable degree of rigidity was seen. In animals with modest rigidity a velocity-dependent increase in muscle resistance and corresponding appearance in electromyographic activity (consistent with the presence of spasticity) was measured during ankle rotation (4-612 degrees /s rotation). Measurement of the H-reflex revealed a significant increase in Hmax/Mmax ratio and a significant loss of rate-dependent inhibition. In the same animals a potent increase in motor evoked potential amplitudes was measured and this change correlated positively with the increased H-reflex responses. Spasticity and rigidity were consistently present for a minimum of 3 months after ischemia. Intrathecal treatment with baclofen (GABA B receptor agonist) and nipecotic acid (GABA uptake inhibitor) provided a significant suppression of spasticity, rigidity, H-reflex or motor evoked potentials. Dorsal L2-L5 rhizotomy significantly decreased muscle resistance but had no effect on increased amplitudes of motor evoked potentials. Confocal analysis of spinal cord sections at 8 weeks-12 months after ischemia revealed a continuing presence of ChAT positive alpha-motoneurons, Ia afferents and VGLUT2 and VGLUT1-positive terminals but a selective loss of small presumably inhibitory interneurons between laminae V-VII. These data demonstrate that brief transient spinal cord ischemia in rat leads to a consistent development of spasticity and rigidity. The lack of significant suppressive effect of dorsal L2-L5 rhizotomy on motor evoked potentials response indicates that descending motor input into alpha-motoneurons is independent on Ia afferent couplings and can independently contribute to increased alpha-motoneuronal excitability. The pharmacology of this effect emphasizes the potent role of GABAergic type B receptors in regulating both the spasticity and rigidity.

Ischemia-reperfusion injury in the spinal cord of rabbits strongly enhances lipid peroxidation and modifies phospholipid profiles.

The effect of spinal cord ischemia (10, 20, and 40 min) and post-ischemic reperfusion (10, 30, and 60 min) on lipid peroxidation and phospholipids was investigated. Spinal cord ischemia was accompanied by lipolytic processes with significant changes in concentration of lipid peroxidation products (LPP). Reestablishment of the blood supply after 10 min ischemia was accompanied by significantly increased levels of thiobarbituric acid reactive substances (TBA-RS) after 10 and 30 min of reperfusion. Following 20 and 40 min ischemia a significant increase was observed at all reperfusion periods. Ischemia itself significantly reduced the concentration of phosphatidyl inositol (IP), phosphatidyl ethanolamine (EP) and ethanolamine plasmalogens (Epls). Significant changes were observed in concentration of phosphatidyl serine (SP) too, but only after 20 and 40 min of ischemia. The concentration of phosphatidic acid (PA) was significantly reduced only after 10 min of ischemia. The onset of reperfusion after ischemia was accompanied by a diverse pattern of changes in PA, IP, Epls and SP, while the concentration of EP remained at the above mentioned ischemic intervals.

Localization of NADPHd-exhibiting neurons in the spinal cord of the rabbit

Segmental and laminar distributions of nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd)‐exhibiting neurons were examined in the rabbit spinal cord by using horizontal, sagittal, and transverse sections. A large number of NADPHd‐positive neurons in the spinal cord of rabbit appeared to fall into six categories (N1–N6), but others could not be classified. Major cell groups of NADPHd‐exhibiting neurons were identified in the superficial dorsal horn and around the central canal at all spinal levels and in the intermediolateral cell column at thoracic and upper lumbar levels. NADPHd‐exhibiting neurons of the pericentral region were divided into a thin subependymal cell column containing longitudinally arranged, small bipolar neurons with processes penetrating deeply into the intermediolateral cell column and/or running rostrocaudally in the subependymal layer. The second pericentral cell column located more laterally in lamina X contains large, intensely stained NADPHd‐exhibiting neurons with long dendrites radiating in the transverse plane. In the pericentral region (lamina X), close association of NADPHd‐exhibiting somata and fibers and mostly longitudinally oriented blood vessels were detected. Neurons of the sacral parasympathetic nucleus, seen in segments S1–S3, exhibited prominent NADPHd cellular staining accompanied by heavily stained fibers extending from Lissauers tract through lamina I along the lateral edge of the dorsal horn to lamina V. A massive dorsal gray commissure, highly positive in NADPHd staining, was found in segments S1–S3. Scattered positive cells were also found in the deeper dorsal horn, ventral horn, and white matter. Fiberlike NADPHd staining was found in the superficial dorsal horn and pericentral region in all the segments studied. Dense, punctate, nonsomatic NADPHd staining was detected in the superficial dorsal horn, in the pericentral region all along the rostrocaudal axis, and in the nucleus phrenicus (segments C4–C5), nucleus dorsalis (segments Th2–L2), Onufs nucleus (segments S1–S3), and the dorsal part of the dorsal gray commissure (S1–S3). J. Comp. Neurol. 406:263–284, 1999.

Improvement of energy state and basic modifications of neuropathological damage in rabbits as a result of graded postischemic spinal cord reoxygenation

The role of graded postischemic reoxygenation applied at the end of 20 min of spinal cord ischemia was studied with respect to the intraspinal pO2 tension, energy state, and histopathological sequelae. Graded postischemic reoxygenation can induce a positive shift in the intraspinal pO2 tension, but normal postischemic reoxygenation with normotensive pO2 blood tension inevitably causes the postischemic intraspinal pO2 overshoot. Graded postischemic reoxygenation significantly improves the energy state expressed by higher adenosine triphosphate (ATP), phosphocreatine (PCr) and glucose levels. Using the Nauta impregnating degenerating method, clear histopathological differences were found in the L3-S3 segments after 20 min of ischemia. Apparently divergent damage was observed when normal reoxygenation or graded postischemic reoxygenation was used. Diametrically different histopathological outcomes were obtained with normal reoxygenation and graded postischemic reoxygenation 2 and 4 days postoperatively.

Mapping of the canine lumbosacral spinal cord neurons by nauta method at the end of the early phase of paraplegia induced by ischemia and reperfusion

The Nauta impregnation method was used to map the neuronal changes in the canine lumbosacral segments following ischemia and reperfusion. The early perikaryal changes ensuing during the first phase after 30 min of thoracic aorta cross-clamping alone or followed by 30 min of reperfusion were mapped. During the second phase (one to six postischemic reperfusion days) the dendritic, preterminal and synaptic degeneration developed. The influence of 30 min cross-clamping immediately followed by perfusion fixation is characterized by the occurrence of flocculent argyrophilic clusters in the cytoplasm of middle-sized and large neurons of L3-S1 segments. Declamping of the thoracic aorta followed by 30 min of reperfusion basically modifies the susceptibility of lumbosacral neurons to Nauta impregnation promoting somatic and dendritic argyrophilia mainly of small (less than 15 microns) neurons, localized mostly in the fifth, sixth and seventh layers, respectively. This early appearing somatic and dendritic argyrophilia is not abolished by a pretreatment of sections with acetone in which cholesterol and its esters are highly soluble, or chloroform-methanol which extracts total lipid. After 24 h of reperfusion the somatic and dendritic argyrophilia is lost but the first signs of drop-like degeneration are detected in all but three superficial dorsal horn layers. At the end of the third reperfusion day, an atypical form of bouton degeneration was found, consisting of massive occurrence of enlarged (greater than 4 microns) boutons encircled by a clear halo. Laminar distribution of enlarged degenerating boutons coincides with laminar quantitative distribution of small argyrophilic neurons detected 30 min after reperfusion. The basic orientation of the many terminal fibres attached to enlarged boutons suggests that they belong to the axons localized mainly in the lateral and anterior columns. Despite a dense argyrophilic network pervading the gray matter of lumbosacral segments only pale shadows of middle-sized and large neurons were found at the end of the sixth reperfusion day and neither somatic nor vessel wall argyrophilia could be detected. All animals surviving one, three and six days postoperatively suffered from fully developed paraplegia.

Reduced nicotinamide adenine dinucleotide phosphate diaphorase in the spinal cord of dogs

The distribution of somatic, fibre-like and punctate, non-somatic reduced nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase activity was examined in dog spinal cord using horizontal, sagittal and transverse sections. The morphological features of NADPH diaphorase exhibiting neurons divided into six different neuronal types (N1-N6) were described and their laminar distribution specified. Major cell groups were identified in the superficial dorsal horn and around the central canal at all spinal levels, and in the intermediolateral cell column at thoracic level. NADPH diaphorase exhibiting neurons of the pericentral region were distributed in a thin subependymal cell column containing longitudinally-arranged small bipolar neurons with processes penetrating deeply into the intermediolateral cell column and/or running rostrocaudally in the subependymal layer. The second pericentral cell column located more laterally in lamina X contains large, intensely-stained NADPH diaphorase exhibiting neurons with long dendrites radiating in the transverse plane. Neurons of the sacral parasympathetic nucleus seen in segments S1-S3 exhibited prominent NADPH diaphorase activity accompanied by heavily-stained fibres extending from Lissauers tract through lamina I along the lateral edge of the dorsal horn to lamina V. A massive dorsal gray commissure, with high NADPH diaphorase activity, was found in segments S1-S3. At the same segmental level a prominent group of moderately-stained motoneurons was detected in the dorsolateral portion of the anterior horn. Fibre-like NADPH diaphorase activity was found in the superficial dorsal horn and pericentral region in all segments studied. Punctate, non-somatic NADPH diaphorase activity was detected in the superficial dorsal horn, in the pericentral region all along the rostrocaudal axis and in the nucleus phrenicus (segments C4-C5), nucleus dorsalis (segments Th2-L2), nucleus Y (segments S1-S3), and the dorsal part of the dorsal gray commissure (S1-S3). A schematic diagram documenting the segmental and laminar distribution of NADPH diaphorase activity is given.

Postischemic hypoxia improves metabolic and functional recovery of the spinal cord

We studied the effect of graded postischemic reoxygenation on the tissue concentrations of adenylates, glucose, and lactate in the rabbit lumbar spinal cord after 10, 20, and 30 minutes of ischemia. In comparison with recirculation without manipulated Pao2, a decrease of Pao2 to 40 to 45 mm Hg upon reestablishment of blood circulation after ischemia led to an amelioration of the energy metabolism in the spinal cord tissue as determined by measuring the ATP concentration and energy charge. The protective effect of postischemic hypoxia was also reflected by the improvement of neurologic functions in animals after 10 and 20 minutes of ischemia.