[Measurement of CSF flow in the spinal canal using MRI with an optimized MRI protocol: experimental and clinical studies]

Clinical Outcomes of Surgical Treatment for Arachnoid Web: A Case Series

Introduction

We describe 5 patients who underwent operative treatment for arachnoid web (AW) and discuss the postoperative clinical outcome in each case. AW is an extremely rare disease that causes cord compression and syringomyelia in the thoracic spine. To date, 14 cases only of AW have been reported, and the effect of surgical intervention on clinical and radiologic outcomes is unknown.

Methods

Five patients who underwent surgical treatment for AW were retrospectively reviewed. The clinical outcomes were evaluated using the thoracic Japanese Orthopaedic Association (T-JOA) score. Preoperative and postoperative images were reviewed.

Results

All the patients presented with spastic gait and numbness in the lower extremities. Two patients also presented with bladder-bowel dysfunction (BBD). AW, or the so-called “scalpel” sign, was seen dorsally in the thoracic spine on magnetic resonance imaging in all the patients. Syringomyelia adjacent to the web was observed in 4 patients. Fenestration and web resection without instrumentation was performed in all the cases. Overall, significant improvement was seen in locomotion and the total T-JOA score postoperatively. However, numbness in the lower extremities improved in 2 patients but was unchanged in 3 cases. BBD was ameliorated in 1 patient but remained unchanged in the other patient.

Conclusions

Our experience suggests that surgical treatment, including the another patient and resection of the web, can correct the flow dynamics of cerebrospinal fluid and allow neurologic recovery, in particular locomotion, in patients with AW.

Intrathecal magnetic drug targeting using gold-coated magnetite nanoparticles in a human spine model

AIM

We aimed to magnetically guide and locally confine nanoparticles in desired locations within the spinal canal to achieve effective drug administration for improved treatment of chronic pain, cancers, anesthesia and spasticity.

MATERIALS & METHODS

We developed a physiologically and anatomically consistent in vitro human spine model to test the feasibility of intrathecal magnetic drug targeting. Gold-coated magnetite nanoparticles were infused into the model and targeted to specific regions using external magnetic fields. Experiments and simulations aiming to determine the effect of key parameters, such as magnet strength, duration of magnetic field exposure, magnet location and ferrous implants, on the collection efficiency of superparamagnetic nanoparticles in targeted regions were performed.

RESULTS

An 891% increase in nanoparticle collection efficiency within the target region was achieved using intrathecal magnetic drug targeting when compared with the control. Nanoparticle collection efficiency at the target region increased with time and reached a steady value within 15 min. Ferrous epidural implants generated sufficiently high-gradient magnetic fields, even when magnets were placed at a distance equal to the space between a patient's epidermis and spinal canal.

CONCLUSION

Our experiments indicate that intrathecal magnetic drug targeting is a promising technique for concentrating and localizing drugs at targeted sites within the spinal canal for treating diseases affecting the CNS.

The frequency and magnitude of cerebrospinal fluid pulsations influence intrathecal drug distribution: key factors for interpatient variability

BACKGROUND

Intrathecal drug delivery is an efficient method to administer therapeutic molecules to the central nervous system. However, even with identical drug dosage and administration mode, the extent of drug distribution in vivo is highly variable and difficult to control. Different cerebrospinal fluid (CSF) pulsatility from patient to patient may lead to different drug distribution. Medical image-based computational fluid dynamics (miCFD) is used to construct a patient-specific model to quantify drug transport as a function of a spectrum of physiological CSF pulsations.

METHODS

Magnetic resonance imaging (MRI) and CINE MRI were performed to capture the patient's central nervous system anatomy and CSF pulsatile flow velocities. An miCFD model was reconstructed from these MRIs and the patient's CSF flow velocities were computed. The effect of CSF pulsatility (frequency and stroke volume) was investigated for a bolus injection of a model drug at the L2 vertebral level. Drug distribution profiles along the entire spine were computed for different heart rates: 43, 60, and 120 bpm, and varied CSF stroke volumes: 1, 2, and 3 mL. To assess toxicity risk for patients with different physiological variables, therapeutic and toxic concentration thresholds for a common anesthetic were derived from experimental studies. Toxicity risk analysis was performed for an injection of a spinal anesthetic for patients with different heart rates and CSF stroke volumes.

RESULTS

Both heart rate and CSF stroke volume of the patient strongly influence drug distribution administered intrathecally. Doubling the heart rate (from 60 to 120 bpm) caused a 26.4% decrease in peak concentration in CSF after injection. Doubling the CSF stroke volume diminished the peak concentration after injection by 38.1%. Computations show that potentially toxic peak concentrations due to injection can be avoided by changing the infusion rate. Using slower infusion rates could avoid high peak concentrations in CSF while maintaining drug concentrations above the therapeutic threshold.

CONCLUSIONS

Our computations identify key variables for patient to patient variability in drug distribution in the spine observed clinically. The speed of drug transport is strongly affected by the frequency and magnitude of CSF pulsations. Toxicity risks associated with an injection can be reduced for a particular patient by adjusting the infusion variables with our rigorous miCFD model.

The effect of pulsatile flow on intrathecal drug delivery in the spinal canal

Clinical studies have shown that drugs delivered intrathecally distribute much faster than can be accounted for by pure molecular diffusion. However, drug transport inside the cerebrospinal fluid (CSF)-filled spinal canal is poorly understood. In this study, comprehensive experimental and computational studies were conducted to quantify the effect of pulsatile CSF flow on the accelerated drug dispersion in the spinal canal. Infusion tests with a radionucleotide and fluorescent dye under stagnant and pulsatile flow conditions were conducted inside an experimental surrogate model of the human spinal canal. The tracer distributions were quantified optically and by single photon emission computed tomography (SPECT). The experimental results show that CSF flow oscillations substantially enhance fluorescent dye and radionucleotide dispersion in the spinal canal experiment. The experimental observations were interpreted by rigorous computer simulations. To demonstrate the clinical significance, the dispersion of intrathecally infused baclofen, an anti-spasticity drug, was predicted by using patient-specific spinal data and CSF flow measurements. The computational predictions are expected to enable the rational design of intrathecal drug therapies.

CARDIAC-GATED PHASE-CONTRAST MAGNETIC RESONANCE IMAGING OF CEREBROSPINAL FLUID FLOW IN THE DIAGNOSIS OF IDIOPATHIC SYRINGOMYELIA

OBJECTIVE

Syringomyelia without an obvious cause, such as a Chiari malformation, a tumor, or a spinal injury, is rare and may be associated with an arachnoid web or cyst. In the literature, conventional myelography is the diagnostic method of choice. In this retrospective study, we evaluated the diagnostic value of magnetic resonance imaging (MRI) cerebrospinal fluid (CSF) flow studies as compared with conventional myelography in patients with syringomyelia.

METHODS

From early 2003 to late 2006, 320 patients with syringomyelia underwent cardiac-gated phase-contrast MRI of CSF flow in the brain and spine. We assessed the presence of CSF flow blockage as well as syrinx site, shape, and size. Additional myelography was performed in 8 patients. CSF flow blockage and progressive neurological symptoms or progression of syringomyelia were indications for surgery.

RESULTS

Syringomyelia without an obvious cause was found in 125 patients. CSF flow blockage was detected in 33 patients. Seven of these patients underwent cyst wall resection and decompression of the subarachnoid space via a unilateral approach without laminectomy. Myelography revealed CSF flow blockage in only 2 of 8 cases. In the other 6 patients, MRI detected a blockage and surgery revealed arachnoid cysts or webs. Postoperative CSF flow studies revealed free CSF flow in all 10 surgically treated patients. In 6 of these patients, syrinx size was reduced after surgery.

CONCLUSION

Myelography should not be the method of choice for the diagnosis of idiopathic syringomyelia. MRI CSF flow studies were found to be more reliable.

Intrathecal Catheter Granuloma Associated with Isolated Baclofen Infusion

Intrathecal (IT) baclofen is an effective management strategy for controlling spasticity in patients unresponsive to maximal oral therapy. We present the case of a 57-yr-old woman who was rendered quadriplegic after a complete spinal cord transection at the C6 level. Her course was complicated by severe spasms, which were uncontrolled despite titrating orally administered baclofen to 80 mg/d. IT baclofen testing was performed with good response, and administration was commenced via an implanted intrathecal pump 6 mo after the injury at an initial dose of 200 microg/d. Catheter revision was required 2 wk later as a result of catheter displacement. The initial IT baclofen dose was gradually increased to achieve good control at a level of 400 microg/d. After a period of stability lasting 38 mo, her lower limb spasms dramatically increased in severity and remained poorly controlled despite repeated dose increases. Contrast pumpogram and computed tomography myelogram were performed to exclude a mechanical cause for this apparent increase in baclofen requirement. These investigations revealed neither catheter displacement nor fracture as suspected but, rather, displayed the presence of a catheter tip-associated mass. Catheter tip granuloma has not previously been described in a patient receiving IT baclofen alone. This suggests that although uncommon, the possibility of catheter-associated granuloma must be considered in all patients receiving IT baclofen presenting with altered neurological function or significant increase in drug requirement.

The clinical application of non-invasive intracranial blood volume pulse wave monitoring

An ultrasonic method was used to non-invasively measure intracranial blood volume (IBV) pulse waveforms. This technology has previously shown a strong association between invasively recorded ICP pulse waves and non-invasively recorded IBV pulse waves. The objective of the present study was to investigate the diagnostic value of non-invasively measured IBV pulse waves in the cases of different pathologies. A total of 75 patients were examined and these included cases of acute, chronic and stabilized hydrocephalus, spinal cord injury and terminal blood flow. These were compared to a control group of 53 healthy volunteers. The object of comparison was normalized and averaged IBV pulse waves. Pathological IBV pulse waveforms were compared with IBV pulse waveforms of the normal group using sub-wave values, the area under waveform curve and the Euclidean distance calculation. The non-invasively measured IBV pulse waveform is not significantly dependent on acoustic path, gender or age. A detectable change in IBV pulse waveform shape was observed in situations when disturbance in intracranial hydrodynamics was present, e.g. during hypoventilation tests, in cases of terminal blood flow and hydrocephaly, depicting the level of hydrocephalus activity and the patient's compensatory capabilities as well as the effect of treatment.

Is the blood-CSF barrier altered in disease?

OBJECTIVE

To illustrate the influence of cerebrospinal fluid (CSF) flow on lumbar CSF protein concentration and to test for an altered blood-CSF barrier permeability as additional influence.

PATIENTS AND METHODS

Consecutively hospitalized patients with normotensive hydrocephalus (n = 21) underwent lumbar puncture with CSF being sampled in sequential portions. CSF/blood quotients of albumin (QAlb) and of immunoglobulin G (QIgG) were compared intra-individually and with calculated values from a reference patient sample.

RESULTS AND CONCLUSIONS

QAlb and QIgG of intra-individual sequential portions correlated highly with each other (median r = 0.95), suggesting lumbar CSF flow as the main thecal determinant of lumbar QAlb and QIgG variation. In addition, QIgG, relative to QAlb, was significantly lower in study patients compared with a reference patient sample (P = 0.002), implying an alteration of the blood-CSF barrier permeability as a minor determinant of QAlb and QIgG variation in study patients.

Considerations in the use of cerebrospinal fluid pharmacokinetics to predict brain target concentrations in the clinical setting: implications of the barriers between blood and brain

In the clinical setting, drug concentrations in cerebrospinal fluid (CSF) are sometimes used as a surrogate for drug concentrations at the target site within the brain. However, the brain consists of multiple compartments and many factors are involved in the transport of drugs from plasma into the brain and the distribution within the brain. In particular, active transport processes at the level of the blood-brain barrier and blood-CSF barrier, such as those mediated by P-glycoprotein, may lead to complex relationships between concentrations in plasma, ventricular and lumbar CSF, and other brain compartments. Therefore, CSF concentrations may be difficult to interpret and may have limited value. Pharmacokinetic data obtained by intracerebral microdialysis monitoring may be used instead, providing more valuable information. As non-invasive alternative techniques, positron emission tomography or magnetic resonance spectroscopy may be of added value.

Imaging in chronic spinal cord injury--indications and benefits

As most patients who have suffered spinal cord injury can now expect a normal life span, the late complications of these injuries are seen increasingly frequently. Regular surveillance of both the renal tract and the central nervous system (CNS) is important as the treatment of impending, potentially fatal complications can be implemented before damage has progressed too far. Renal tract complications are particularly dangerous as they are often clinically silent but regular surveillance to detect early deterioration in renal function, particularly from reversible causes such as reflux or obstruction can pre-empt problems. Follow-up protocols depend on the bladder management regime but most centres advocate regular ultrasound with less frequent isotope function studies. With the increasing ability to diagnose and treat the neurological complications, surveillance of the state of the spinal cord with MRI is also important and many centres now advocate checks every few years with sagittal midline T2W sections are sufficient unless changes are noted, when axial T1W sections can be added without significant examination time penalty. Imaging is critical in acute problems. In addition to suffering from the usual normal conditions, patients with spinal cord injury suffer others peculiar to, or particularly related to, the injury, which may be missed as their symptomatology is greatly altered by their paraplegic or quadriplegic status and they may often present as generally unwell but with no obvious cause. This review discusses the role of radiology in routine surveillance of the CNS and the renal tract as well as in assessing specific conditions such as deteriorating neurology or renal function, pain, spinal instability, pressure sores, ectopic ossification, muscular spasm, spinal instability, airway problems and elective operations on the renal tract.