Subarachnoid fluid of the optic nerve in normal adults

OBJECTIVE

The purpose of the study is to determine the amount of subarachnoid fluid of the optic nerve in normal adults using magnetic resonance (MR) imaging and to investigate whether the subarachnoid fluid is displaced in abduction as assumed by the 30 degree echographic test.

DESIGN

The design was a prospective observation study.

PARTICIPANTS

Twenty-one healthy headache-free adults participated. Ten (48%) were men and 11 (52%) were women with a mean age of 34.3 +/- 7.9 years.

INTERVENTION

Both optic nerves were examined in primary and 45 degrees right and left gazes with T2 fast-spin echo fat-suppressed coronal MR imaging in quadrature head coil. Four MR images, 4 mm apart, starting from 4 mm posterior to the globe were obtained for both nerves simultaneously with an imaging time of 2 minutes and 24 seconds per gaze.

MAIN OUTCOME MEASURES

Optic nerve and sheath diameters were measured.

RESULTS

Mean nerve diameters were 3.2 +/- 0.4 mm anteriorly to 2.6 +/- 0.4 mm posteriorly, and mean sheath diameters were 5.2 +/- 0.9 mm anteriorly to 3.9 +/- 0.4 mm posteriorly. Optic sheath diameters did not change significantly in abduction or adduction.

CONCLUSIONS

Magnetic resonance imaging can be used effectively to determine the amount of subarachnoid fluid of the optic nerve. In normal adults, the amount of optic nerve subarachnoid fluid is variable and may be substantial. The authors' MR findings show that optic nerve subarachnoid fluid is not displaced significantly with abduction or adduction.

The anatomical variations of sylvian veins and cisterns

The anatomical variations of sylvian vein and cistern were investigated during the pterional approach in 750 operative cases with different pathologies. All patients were operated on at the Neurosurgical Department of Ataturk University Medical School, Erzurum, Turkiye. The patients underwent surgery for the lesions necessitating the right or left pterional approach. The findings were recorded during surgical intervention and observed through the operative sketches of the pathologies, the slides, and videotapes of the operations. In our study, we surgically classified the variations of sylvian vein, according to its branching and draining patterns. Type I: The fronto-orbital (frontosylvian), fronto-parietal (parietosylvian) and anterior temporal (temporosylvian) veins drain into one sylvian vein. Type II: Two superficial sylvian veins with separated basal vein draining into the sphenoparietal and Rosenthal's basal vein. Type III: Two superficial sylvian veins draining into the sphenoparietal and the superior petrosal veins. Type IV: Hypoplastic superficial sylvian vein and the deep one. Four types of sylvian vein variations were defined as follows. The type I was seen in 52.8% (n = 396), the type II was found in 19.2% (n = 144), type III was recorded in 18.2% (n = 137), and type IV, or hypoplastic and deep form was discovered in 9.8% (n = 73) of patients. The coursing of sylvian vein was in the temporal side (Temporal Coursing) in 62.4 percent of the cases (n = 469), in the frontal side (Frontal Coursing) in 25 % of the patients (n = 187) and in 9 percent of the cases (n = 67) in the deep localization (Deep Coursing). Only 3.6% of the cases (n = 27) showed Mixed Coursing. The variations of the sylvian cisterns were classified into three types, according to the relationships between the lateral fronto-orbital gyrus and the superior temporal gyrus. In Sylvian type, the frontal and temporal lobes are loosely (Sylvian Type A, wide and large) or tightly (Sylvian Type B, close and narrow) approximated on the surface thereby covering the substance of the sylvian cistern. In Frontal Type, the proximal part of the lateral fronto-orbital gyrus herniated into the temporal lobe. In Temporal Type, the proximal part of the superior temporal gyrus herniated into the lateral fronto-orbital gyrus. The variations of the sylvian cisterns in 750 patients with different pathologies, were as follows: in 47.7% (n = 358) Sylvian type A, in 27.2% percent (n = 204) Sylvian type B, in 16.3% (n = 122) frontal type and in 8.8% (n = 66) temporal type. We concluded that venous perfusion discorder of the brain is the most important factor during the pterional approach. Careful intraoperative assessment and protection of the sylvian vein, which is a surgical pitfall, is an indispensable part of the operation. The recognition of the anatomical variations of the sylvian vein and cistern, and the detailed knowledge of the microvascular relationships and the importance of preservation of this vein at that level, will allow the neurosurgeon, believing in the minimally invasive neurosurgical techniques, to construct a better and safer microdissection plan, to save time, and can prevent postoperative neurological deficits.

A new combined spinal-epidural apparatus: measurement of the distance to the epidural and subarachnoid spaces

A new combined spinal-epidural anaesthesia apparatus with a 27G lockable spinal needle was used in 151 patients. Two groups could be created, based on whether dural perforation was felt or not (group 1: with dural click; group 2: no dural click). Measurements of the epidural space depth and of the protrusion of the spinal needle from the epidural needle (tip-to-tip distance) were made. The mean depth of the epidural space was 5.59 cm. Correlations were found with body weight, weight-to-height ratio and body mass index (p < 0.001). The mean tip-to-tip distance measured was 7.0 mm in the patients of group 1, whereas in group 2 a distance of 8.9 mm was found. This difference was statistically significant. Correlations were found between the epidural space width and the patient's height, weight-to-height ratio and body mass index. Four patients felt paraesthesia during placement of the spinal needle and, in another four patients, aspiration was necessary to detect cerebrospinal fluid. Two patients needed epidural top-ups due to insufficient level of anaesthesia. The lockable spinal needle provides safe and stable conditions during injection and a high rate of success in reaching the subarachnoid space.

Magnetic resonance imaging contrast media in the subarachnoid space. A comparison between gadodiamide injection and gadopentetate dimeglumine in an experimental study in pigs

RATIONALE AND OBJECTIVES

The authors studied the neural tolerance and contrast enhancement of a nonionic, gadodiamide injection (gadolinium [Gd]-DTPA-BMA), and an ionic, gadopentetate dimeglumine (Gd-DTPA), contrast medium in the subarachnoid space of the pig.

METHODS

Sixteen experiments were performed in eight pigs. Lumbar and lateral C1-C2 punctures were performed. Ten milliliters of Gd-DTPA-BMA or Gd-DTPA with Gd concentrations varying from of 500 mmol/L to 0.625 mmol/L were injected, in four experiments via the lumbar route and in 12 experiments via the C1-C2 puncture.

RESULTS

Four pigs injected via the C1-C2 puncture with a Gd concentration of 500 mmol/L had signs of somatomotor irritation and all were paretic after 24 hours. No somatomotor effects were observed in the other experiments, where lower concentrations of Gd were used. Marked enhancement of the cerebrospinal fluid with no visible signal differences was obtained with concentrations from 10 to 0.625 mmol/L.

CONCLUSIONS

Both Gd-DTPA-BMA and Gd-DTPA are remarkably well tolerated in the subarachnoid space. In doses relevant for imaging purposes no adverse effects were seen.

The cochlear aqueduct in pediatric temporal bones

The cochlear aqueduct is a bony channel which contains the fibrous periotic duct and connects the perilymphatic space of the basal turn of the cochlea with the subarachnoid space of the posterior cranial cavity. Previous histological studies suggested that patency depended on age, whereas a more recent study showed no statistical correlation between age and patency. To clarify patency in pediatric cochlear aqueducts, we selected 21 temporal bones from 12 infants and children, varying in age from birth to 9 years, in which the cochlear aqueduct was fully visible on one histological section. Photographs were taken for documentation and the length and width of the orifice of the external aperture of the aqueduct at the scala tympani were measured and followed to the internal aperture at the subarachnoid space. The lumen of the duct was examined for mononucleated cells, blood cells and fibrous tissue. Measurements revealed that the mean length of the cochlear aqueduct was 4.6 mm (range, 2.4-10.7 mm), mean width of the external aperture was 484 microm (range, 225-869 microm), and mean width of the internal aperture was 1293 microm (range, 699-2344 microm). The mean diameter of the narrowest part (isthmus) was 151 microm (range, 75-244 microm). In all temporal bones the cochlear aqueduct was patent, with one exception. This latter temporal bone was from a 2-month-old girl with multiple intralabyrinthine anomalies, with the missing cochlear aqueduct believed to be due to an aplasia. Our results support prior measurements of the cochlear aqueduct and demonstrate a short and patent cochlear aqueduct in newborns. With growth, a significant increasing length of the duct was found.

Microanatomical basis for the third ventriculostomy

In the last few years, there has been a resurgence of interest in endoscopic third ventriculostomy as a treatment for obstructive hydrocephalus. Although various techniques have been used to perform this procedure, not enough emphasis has been placed on the microanatomical details of the third ventricle and surrounding cisterns in relation to this procedure. Using a surgical microscope we examined the microsurgical anatomy of the floor of the third ventricle floor and related subarachnoid cisterns in 20 adult brains using the "immersion technique" in conjunction with microsurgical dissection. We believe that the optimal place to fenestrate is the midline of the floor of the third ventricle, behind the infundibular recess and in front of the mammillary bodies, communicating the third ventricle with the anterior interpeduncular cistern, minimizing the risk for vascular lesions. Stereotactic third ventriculostomy is a safe and effective way of re-establishing normal cerebrospinal fluid flow dynamics in selected cases of obstructive hydrocephalus. However, in an endoscopic exposure only a small portion of the anatomy can be seen at any one time, and important neurovascular structures may be located adjacent to the endoscope, but outside of the visual range of the lens. A thorough understanding of the microanatomy of the neural and vascular structures surrounding the third ventricle and related cisterns is essential in order to improve surgical results avoiding complications.

A clinical measure of the posterior epidural space depth

BACKGROUND AND OBJECTIVES

The object of this study was to measure the clinically relevant depth of the posterior epidural space (ES) while placing subarachnoid catheters.

METHODS

"Hanging drop" technique was used to locate the ES via a midline approach in the lumbar area. The distance from the skin to the ES was measured, and the needle was advanced until free flow of cerebrospinal fluid was observed. The distance between entry into the ES and the subarachnoid space-the posterior ES depth-was then measured. Regression analysis was used to investigate relationships between skin-to-ES distance, posterior ES depth, and patient characteristics (height, weight, body surface area [BSA] and age).

RESULTS

The 55 patients studied had a mean skin-to-ES distance of 50.9 +/- 12 mm (range, 27-94) and a mean posterior ES depth of 6.9 +/- 4 mm (range 2-25). Skin-to-ES distance was related to BSA (r = .597, P < .0001) and weight (r = .572 P < .0001). No correlation was found between posterior ES depth and any other variable.

CONCLUSIONS

The posterior ES has been found to be somewhat larger and more variable than previously described. The findings provide clinical confirmation of recent radiologic and cadaveric studies, which portray a posterior ES of variable size and complex shape. These findings have implications for cannulation and use of epidural therapy as well as for the combined catheter epidural and single-dose spinal technique.

Microsurgical anatomy of the arachnoidal trabecular membranes and cisterns at the level of the tentorium

A clear and thorough understanding of the neuroanatomical structures of the subarachnoid cisterns is important because they provide natural pathways to intracranial arteries, veins, and nerves during microvascular procedures without disturbing surrounding important brain structures. Using a surgical microscope, we examined the microsurgical anatomy of the trabecular membranes and subarachnoid cisterns in 20 adult cadaver brains. The brains were immersed in Ringer's solution and air was injected into the subarachnoid cisterns while the brains remained submerged in solution. We identified seven trabecular membranes that limit six cisterns. We specifically looked at the anatomical relationship between the trabecular membranes and cisterns and their corresponding vessels and cranial nerves. The cistern divisions and the dispositions of trabecular membranes were closely related to the vascular division patterns of the principal brain arteries.

Microsurgical anatomy of the infratentorial trabecular membranes and subarachnoid cisterns

The understanding of the anatomy of the subarachnoid cisterns and trabecular membranes is of paramount importance in the surgical treatment of pathology of the posterior fossa. Aneurysms, arteriovenous malformations, and some tumors should be approached through the subarachnoid space. The subarachnoid cisterns provide natural pathways to approach neurovascular and cranial nerve structures. The microsurgical anatomy of the infratentorial subarachnoid cisterns was studied in twenty adult brains, using the 'immersion technique'. Air was injected into the subarachnoid cisterns and brains were dissected under the operative microscope. Six main compartmental trabecular membranes were identified in the infratentorial level. They divide the subarachnoid space into six cisterns. Cisternal divisions and the disposition of the trabecular membranes were closely related to the vascular divisional patterns of the principal arteries. Thorough knowledge of the microsurgical anatomy of the subarachnoid space will aid neurosurgeons during the surgical approach of many vascular and tumoral lesions located in the posterior fossa.

A numerical investigation into factors affecting anesthetic distribution during spinal anesthesia

The factors affecting distribution of anesthetic within the spinal column are of current interest due to recent reports of neurological injury occurring during spinal anesthesia. This paper describes a numerical model for simulating anesthetic dispersion, and applies the model to the evaluation of spinal-column size, anesthetic injection rate, and catheter orientation as factors influencing the anesthetic distribution. The model is based upon the finite-element method and incorporates a three-dimensional geometry derived from images of human spinal columns. Simulation results show that the ratio of the cross-sectional dimension of the subarachnoid space within the spinal column to the diameter of the catheter is a critical parameter, with low values of this ratio producing the most uniform anesthetic distributions. Increasing injection rate is found to produce a less uniform distribution in a global sense (higher total volume of anesthetic in the 'sacral' half) but a more uniform distribution in a localized sense (lower concentrations at critical points). Finally, the anesthetic distribution is demonstrated to be highly sensitive to orientation angle at high injection rates.

Posterior fontanelle cranial ultrasound: anatomic and sonographic correlation

OBJECTIVE

The purpose of this study was to correlate normal brain anatomy as seen on posterior fontanelle cranial sonography with anatomical sections of the premature infant brain.

MATERIALS AND METHODS

Images obtained from 93 cranial ultrasound examinations performed via both the anterior and posterior fontanelle in 53 infants, ranging in gestational age from 24 to 42 weeks, were reviewed to determine the ultrasound anatomy visible and also the changing appearances with increasing gestational age. The brains of five infants were sectioned at post-mortem according to predetermined anatomical landmarks to correlate with posterior fontanelle ultrasound scan planes. Brain preservation techniques involved fixation in formalin at room temperature, refrigeration of brain following formalin fixation, and brain freezing at -17 degrees C.

RESULTS

In the premature infant brain, the subarachnoid space is up to 15 mm in thickness. Occipital lobe anatomy well seen includes occipital horns of lateral ventricles, and white matter tracts to the visual cortex and visual association areas. Brain anatomy was better appreciated on sections obtained following brain freezing rather than formalin fixation.

CONCLUSION

Satisfactory ultrasound anatomic correlation of the premature brain is possible using a brain freezing preservation technique. Posterior fontanelle ultrasound allows detailed illustration of occipital lobe anatomy.

Fibrous structures in the subarachnoid space: a study with spinaloscopy in autopsy subjects

The lumbar and lower thoracic subarachnoid space of 26 human autopsy subjects was studied using rigid endoscopy, spinaloscopy. Fibrous attachments were found between nerve roots and/or nerve roots and the arachnoid membrane at least at one spinal level in 16 subjects. The appearance and density of the structures varied, and caused restriction of nerve root mobility in nine subjects. In three of them, the impeded mobility prevented the nerve root from yielding to the contact and pressure exerted either by the tip of the endoscope or by a spinal needle introduced into the subarachnoid space. In another three subjects, a distinct membranous structure was identified in the posterior midline of the subarachnoid space in the lower thoracic and upper lumbar regions. These findings may possibly be associated with the variation in the extent of subarachnoid block and to the development of isolated nerve root trauma in connection with this procedure.

Influence of the subarachnoid position of microcatheters on onset of analgesia and dose of plain bupivacaine 0.5% in continuous spinal anesthesia

BACKGROUND AND OBJECTIVES

Many factors have an impact on the outcome of continuous spinal anesthesia (CSA) with small-bore catheters. Recent publications of neurologic complications after CSA suggest that the local anesthetic as well as the microspinal catheter influence the analgesic effect in CSA. This prospective study was designed to evaluate the influence of the subarachnoid position of 28-gauge spinal catheters on the speed of onset of analgesia and on the dose of plain bupivacaine 0.5% required for a block at the level of T-10 in CSA.

METHODS

Sixty-eight patients (mean age 61.7 +/- 6.4 years) received CSA using a 22-gauge Quincke needle (Kendall, Mansfield, MA) and a 28-gauge spinal catheter. After initial injection of 2.5 mL (minimum) up to a maximum of 5 mL of supplemental doses of plain bupivacaine 0.5%, the time of onset of analgesia at the level of T-10 and the dose of local anesthetics required for this block were determined. The subarachnoid catheter position was examined radiographically by a dye supported conventional anteroposterior roentgenogram of the lumbar spine on the first day after the operation.

RESULTS

The onset time of analgesia and the dose of plain bupivacaine 0.5% required for the block at the level of T-10 were significantly dependent on the subarachnoid position of the microcatheters (P < .01), but not on the level of the lumbar dural puncture (P = .29, P = .69). In patients with cranially running catheters or catheters with the tip at the level of the puncture site, analgesia onset was faster and required doses of bupivacaine were smaller than in patients with caudally running catheters.

CONCLUSIONS

The subarachnoid position of a 28-gauge microcatheter is an important factor with regard to the effectiveness (e.g., onset time of analgesia and dose requirement) of CSA using plain bupivacaine 0.5%.

CSF drains directly from the subarachnoid space into nasal lymphatics in the rat. Anatomy, histology and immunological significance

Cerebrospinal fluid (CSF) drainage pathways from the rat brain were investigated by the injection of 50 microliters Indian ink into the cisterna magna. The distribution of the ink, as it escaped from the cranial CSF space, was documented in 2 mm thick slices of brain and skull cleared in cedar wood oil and in decalcified paraffin sections. Following injection of the ink, deep cervical lymph nodes were selectively blackened within 30 min and lumbar para-aortic nodes within 6 h. Within the cranial cavity, carbon particles accumulated in the basal cisterns but were also distributed in the paravascular spaces around the middle cerebral arteries and the nasal-olfactory artery. Carbon particles in the subarachnoid space beneath the olfactory bulbs drained directly into discrete channels which passed through the cribriform plate and into lymphatics in the nasal submucosa. Although ink was distributed along the subarachnoid space of the optic nerves and entered the cochlea, the nasal route was the only direct connection between cranial CSF and lymphatics. Arachnoid villi associated with superior and inferior sagittal sinuses were identified and a minor amount of drainage of ink into dural lymphatics was also observed. This study demonstrates the direct drainage of cerebrospinal fluid through the cribriform plate in anatomically defined channels which connect with the nasal lymphatics.(ABSTRACT TRUNCATED AT 250 WORDS)

Normal imaging anatomy of the suprasellar cistern and floor of the third ventricle

This article discusses the gross, functional, and imaging anatomy of the suprasellar cistern and its contents as well as the structures that form its borders, among the most important being the floor of the third ventricle and associated structures. Specific structures discussed include the optic chiasm and optic tracts, the anterior third ventricle, the tuber cinereum, the pituitary stalk (infundibulum), the choroidal fissure, the lamina terminalis, the gyrus rectus, the uncus, and the cerebral peduncles.

Cerebrospinal fluid flow. I. Physiology of cardiac-related pulsation

Cardiac-related motion of the cerebrospinal fluid (CSF) was investigated by analysis of the velocity-dependent phase of CSF protons and flow-dependent signal enhancement in magnitude images using ECG-gated FLASH sequences. In the cerebral aqueduct, CSF flow from the third to the fourth ventricle begins 200 ms after the R-wave of the ECG and simulates an arterial pulse wave pattern. It lasts about 60% of the cardiac cycle and is followed by backflow from the fourth to the third ventricle, which is slower and shorter. In the spinal canal, oscillating caudad motion precedes flow from the third to the fourth ventricle by about 50-100 ms and is superimposed on a bulk flow, which moves simultaneously in opposite directions in separate subarachnoid channels; it is directed mainly caudally in the anterior cervical subarachnoid space.

Topographic anatomy of preformed intracranial spaces

This article gives descriptions and measurements of the cerebral ventricles, especially our measurements of the interventricular foramen and the third ventricle. Included are measurements of previous and recent research. The results of endoscopic reviews of the lateral, third and fourth ventricles are also discussed. The subarachnoid spaces are described and illustrated by our corrosion casts. During endoscopic inspection of the subarachnoid spaces, the transcisternal veins are extremely vulnerable. Therefore, these veins in the anterior, middle and posterior cranial fossae are described.

Cerebrospinal fluid flow. II. Physiology of respiration-related pulsations

Cerebrospinal fluid (CSF) flow in the cerebral aqueduct and spinal canal was analysed using real-time magnetic resonance imaging measurement techniques. Respiration-induced rhythmic modulation of the cardiac-related oscillating CSF pulsation in the cerebral aqueduct and spinal canal was found. Deep inspiration was immediately followed by a marked increase in downward CSF flow in the cervical spinal canal, whereas a delay of about two heart beats was seen before downward flow from the third to the fourth ventricle increased. This pattern was also detected during yawning and was followed by a marked increase of blood flow in the internal jugular vein.

MR imaging of normal rat brain at 0.35 T and correlated histology

A custom-built small-animal transceiver was used for in vivo imaging of normal rat brain at 0.35 T, with the objective of identifying anatomic components by comparison of images with corresponding histologic sections. The cerebrum, cerebellum, brain stem, ventricles, hippocampus, and subarachnoid space were identified and cerebrospinal fluid (CSF) was differentiated from gray matter and white matter on coronal and transaxial magnetic resonance (MR) images. These images compare favorably with those obtained by others at higher field strengths in regard to delineating major neuroanatomic structures. It is concluded that this technique will be useful for investigating small-animal models of human neurologic disease involving morphologic and morphometric changes in gray matter, white matter, and CSF-filled spaces.

Long-term, open catheterization of the spinal subarachnoid space for continuous infusion of narcotic and bupivacaine in patients with "refractory" cancer pain. A technique of catheterization and its problems and complications

The technique of long-term, open catheterization of the spinal subarachnoid space for infusion of analgesics in patients with refractory cancer pain is sparsely reported in the literature. We report on a technique using 18G Portex nylon catheters and 16G-17G Tuohy needles, and its problems and complications. One hundred fifty-seven catheters were inserted in 142 patients, in most of them (79%) under deep sedation and local anesthesia. Attempts were made to place the catheter tip as close to the painful segments as possible. The catheters were tunneled subcutaneously (87% of them paravertebrally, over the shoulder, and further parasternally to the third chondrocostal cartilage). The Luer connections of the catheters were fixed to the patients' skin with monofilament steel sutures of dimension 0 and connected to a bacterial filter. At the end of the procedure, 10 ml isotonic saline was injected intrathecally to prevent postspinal puncture headache. Absorbent and impermeable dressings were applied over the tunnel exit, catheter Luer connection and bacterial filter. Antibiotics were given on the day of insertion and 2 days thereafter. During the insertion procedure, the following problems and complications were encountered; two or more attempts before successful spinal-dural puncture (32%), accidental puncture of an extradural vessel (10%), difficult dural puncture (18%), absence of free dripping of cerebrospinal fluid (CSF) in spite of successful dural puncture (4%), blood-stained CSF (9%), radicular pain and paresthesiae (4%), difficult advancement of the catheter (6%), difficult tunneling (11%), and bleeding in the tunnel (0.7%).(ABSTRACT TRUNCATED AT 250 WORDS)

Immunological and neuropathological significance of the Virchow-Robin space

The anatomy of the Virchow-Robin space is reviewed and attention is drawn to its importance as a compartment which is in communication with lymphatic channels of the head and neck and in which local immunological reactions take place. Macrophages in the Virchow-Robin spaces express MHC class II antigens and are well placed to interact with lymphocytes derived from the blood in initiating and promoting immune response to foreign antigens in the brain. The immunological reactions taking place in the Virchow-Robin spaces in encephalitis, multiple sclerosis and human immunodeficiency virus encephalitis are examined for the light they may throw on the pathogenesis of these conditions.

[Measurement of subarachnoid space with a short TR gradient echo method; myelo MRI]

The cerebro-spinal fluid in the subarachnoid space is delineated clearly with gradient field echo technique (TR = 60 ms, TE = 20 ms, flip angle = 20 degrees). Average area, width, depth, and curvature of the subarachnoid space in the cervical region were obtained in ten young normal subjects.