Smal animal SC disease Flashcards
Typical age and breeds for FCEM?
most common in young adult dogs of the larger breeds of dogs:
miniature schnauzer, Labrador retriever,
boxer breeds
Dog: 2 months to 13 years and 5 months, with a median of 4–6 years in the majority of studies
Cats: DSH
from 6 months to 17 years (median, 10 years)
Why are some animals very painful at the onset of FCEM?
Central neurogenic pain refers to spontaneous pain associated with CNS parenchymal lesions that do not involve the meninges. Acute spinal cord injury or ischemia may be related to spontaneous pain in addition to some loss of sensory function caudal to the lesion. The extreme discomfort exhibited by some dogs at the onset of spinal cord ischemia associated with fibrocartilaginous embolism may well be an example of spontaneous central neurogenic pain. The pathophysiology of this form of pain is poorly understood, but disinhibition of dorsal gray column neuronal cell bodies that project into the spinothalamic pathway or a disturbance of the lateral spinothalamic tract, the ventral spinothalamic tract, or both, which results in spontaneous discharge, are possible explanations.
4 hypothesis of embolus entering the vasculature in FCEM
1) Direct penetration of nucleus pulposus fragments into spinal cord or vertebral vessels
2) Chronic inflammatory neovascularization (arterial and venous) of the degenerated
intervertebral disc
3) Presence of embryonic remnant vessels within the nucleus pulposus (which is normally
avascular in adults)
4) Mechanical herniation of nucleus pulposus into the vertebral bone marrow sinusoidal venous channels, with subsequent retrograde entrance into the basivertebral vein
and internal vertebral venous plexus. (Schmorl’s node)
What is a Schmorl node?
intervertebral disc material in the marrow of the vertebral bodies (one of proposed mechanisms for FCEM, common in humans, rare finding in dogs)
Where does nephroblastoma usually occur in the dog, and what is the typical signalment?
T 10-L 2 SCS
Intradural-extraparenchimal
Dogs younger than 2,5 years old
Why does a nephroblastoma usually always involve SCS T10-L2)
correlates with the site of embryonic renal development from intermediate mesoderm and the embryonic mesonephros.
Most common cause of infectious myelitis in dogs?
Canine distemper virus. Other infectious diseases are caused by protozoal agents (Toxoplasma gondii, Neospora caninum), Rickettsia species, and fungal agents.
Most common isolates from dogs with discospondylitis?
Staphylococcus pseudintermedius is the most common isolate. Streptococcus species and Escherichia coli have also been isolated in this lesion. Be aware that, particularly in intact male and female dogs, Brucella canis has been identified in these infections and that it is contagious to humans.
Aspergillus spp.- German Shepherd Dogs
MST for dogs with nephroblastoma?
70 days (one study) - 374 (another)
BrewerD.M,Cerda-GonzalezS,DeweyC.W,et al.Spinal cord nephroblastoma in dogs: 11 cases (1985-2007).J Am Vet Med Assoc.2011;238:618–624.
Where do 80% of IVD extrusion occur in the dog? Why?
T10 and L3 vertebrae
This may relate to the increased motion of the vertebral column at this level compared with the more stable thoracic area. In addition, between the first 10 thoracic vertebrae, an intercapital ligament courses transversely across the dorsal surface of the intervertebral disc to connect the heads of the ribs where they articulate with both adjacent vertebrae. This is an added support to the articulation of the vertebral bodies and may help to prevent intervertebral disc herniation or protrusion between thoracic vertebrae cranial to T10.
In which domestic species is lymhoma the most common vertebral neoplasia?
Cats and cattle
Most common region for lymphoma in the spinal cord?
Thoracolumbar, usually restricted to 1-3 foramina
Typical dog breeds for deg. Myelopathy?
German shepherd dog
boxer,
Cavalier King Charles spaniel,
Pembroke Welsh corgi,
kuvasz,
Bernese mountain dog.
4 stages of DM based on clinical signs?
- Ambulatory pelvic limb UMN paresis and GP ataxia
- Nonambulatory paraparesis and GP ataxia to paraplegia with areflexia in the pelvic limbs, mild muscle atrophy, and some incontinence
- LMN paraplegia with thoracic limb paresis and ataxia
- LMN tetraplegia, severe atrophy, dysphagia, and tongue paresis
Typical breeds and signs of SAD
Pug dogs and french bulldogs
GP ataxia and UMN paresis, affected dogs often have fecal incontinence and have a low tail carriage
Wat is shown in the image? Multiple Afghan hounds from the litter are recumbant, with a spastic paraparesis and GP ataxia of the pelvic limbs. They are 8 MO
A microscopic section of the C8 spinal cord segment from a young Afghan hound with myelinolysis. Note the sparing of the fasciculus proprius and the nerve roots.
Afghan hound myelinolytic encephalomyelopathy is inherited as an autosomal recessive gene disorder. It is a unique primary demyelination that causes necrosis of myelin but spares the axons. It appears to start in the myelin in the midthoracic spinal cord segments and to progress cranially and caudally. The clinical signs begin with mild pelvic limb spastic paresis and ataxia and loss of control of the trunk muscles by 7 to 10 days. They are followed by thoracic limb spastic paresis and ataxia and then recumbency by about 14 to 21 days. The initial onset of clinical signs ranges between 3 and 13 months of age. The myelinolytic lesion is bilaterally symmetric in all the funiculi but spares the fasciculus proprius. The “naked” demyelinated axons float unsupported in their funiculi among a plethora of lipid-filled macrophages. One of the earliest publications on this disorder erroneously explained this lesion as a vascular compromise. Primary demyelination with axonal sparing cannot be caused by any known vascular disorder. The unique distribution of this lesion is unexplained. Most of these dogs also have the same primary demyelination of the axons that surround the dorsal nucleus of the trapezoid body. No clinical signs have been associated with the lesion in the trapezoid body. This inherited myelinolytic disorder was confirmed at autopsy in the dogs in this litter. MRI studies of these dogs have not been described.
Which vertebral body has a high chance of fracture and why?
Cranial aspect of the body of C2 (axis)
This may be the result of the physical stress that is placed there, where the dens articulates with the atlas. The latter acts as a fulcrum when flexion of the head and neck is forced. In addition, the presence of two growth plates in the cranial portion of the body of the axis may be a risk factor for a fracture there.
Name the ossification centres of the axis
- Center 1 - cranial articular surface of the axis body and the dens.
- Intercentrum 1 - for the ventral arch (body) of the atlas.
- Centrum of proatlas: small apex of the dens.
- Intercentrum 2: narrow ossification center between the ossification centers of centrum 1 and centrum 2.
- Centrum 2: central region of the body of the axis.
Which ligaments participate in the normal alignment between atlas and axis?
1) transverse ligament of the atlas - attached on both sides of the ventral arch of the atlas and passes dorsal to the dens
2) dorsal longitudinal atlantoaxial ligament - dorsal arch of the atlas and the spine of the axis
3) apical and two lateral (alar) ligaments - attach the apex of the dens to the basioccipital bone cranially
Where are the pathological lesions with “inherited encephalomyelopathy and polineuropathy” of rotweilers located?
The spinal cord lesion consists of a bilateral symmetric axonopathy with secondary demyelination and astrogliosis, which is most pronounced in the lateral and ventral funiculi. This lesion is not limited to the spinocerebellar tracts. Many tracts are affected, including the UMN tracts, which is why the gait disorder is typical for a dysfunction of the GP and UMN systems. The thoracolumbar segments are most affected, which possibly suggests where the degenerative lesion first develops and explains why the clinical signs are first observed in the pelvic limbs. Vacuolation of neuronal cell bodies is scattered through the spinal cord and brain, with no other evidence of any microscopic abnormality of these neurons. The brains of these dogs test negative for prion protein. A neuropathy is prominent in the recurrent laryngeal nerves and scattered in other long nerves. Denervation atrophy of all the intrinsic laryngeal muscles except for the cricothyroideus is significant
Neuro signs in “inherited encephalomyelopathy and polineuropathy” of rotweilers
The clinical signs begin at about 6 to 8 weeks of age and may start with either inspiratory dyspnea or paraparesis and pelvic limb ataxia. Some of the dogs that first exhibited the signs of laryngeal paralysis had laryngeal tie-back surgery to improve their breathing before the clinical signs were first observed in the pelvic limbs. It is paramount that the veterinary surgeon be aware of this disorder and counsels the owner appropriately before surgery. All dogs progress in a few weeks to tetraparesis and ataxia in all four limbs. Some dogs develop megaesophagus and regurgitate, and some dogs have bilateral microphthalmia. These small eyes appear to be sunken into the orbits, and therefore the third eyelids become prominent. Horner syndrome does not occur in these dogs. A few dogs have been reported to exhibit clinical signs of dysfunction of the cerebellum or the vestibular system
Name the inherited neurodegenerative disorders of the Rottweiler breed
1) inherited encephalomyelopathy and polineuropathy
2) neuroaxonal dystrophy
3) leukoencephalomyelopathy
4) motor neuron disease
5) polyneuropathy (axonopathy)
6) distal neuropathy
7) dystrophynopathy (Duchane type of muscular dystrrophy)
Which nerves innervate the lateral scapular muscles (eg. Atrophy of lateral scapular muscles seen in dogs with disk associated spondlomyelopatyhy)
C6-7 SCS - suprascapular nerve (supraspinatus and infraspinatus m.) and subscapular nerve (subscapular muscle)
Which storage disease is most common in West highland white terriers and Cairn terriers?
Globoid cell leukodystrophy (Krabbes disease)
Which enzyme is deficient in Globoid cell leukodystrophy?
Galactosylceraminase-1 (Beta galactocerebrosidase)
Accumulation of galactosylsphingosine (psychosine)
What is the most likey DD? (See image)
2 month old Cairn terrier with signs of a progressive gait disorder that initially affected the pelvic limbs and progressed to tetraparesis with sublte cerebellar signs
Globoid cell leukodystrophy (Krabbes disease)
Galactosylceramidase 1 deficiency (accumulation of galactosylsphingosine)
Expression of which retrogene is associated with premature/accelerated IVD degeneration in dogs?
fibroblast growth factor 4 (FGF4) retrogene on chromosome 12 in chondrodystrophic breeds
*
This process, called Hansen type I intervertebral disc extrusion (IVDE), also occurs in non-chondrodystrophic breeds at a much lower frequency, and unassociated with the FGF4 retrogene.
Sensitivity of MRI for IVDD diagnosis?
> 98.5%
Benefits of MRI for IVDD diagnosis?
- enhanced diagnostic performance over CT in dogs with peracute signs,
- differentiating disc extrusion from protrusion.
- Residual compression after surgery also can be detected
- prognostication.
MRI prognostic factors for worse locomotor outcome and development of progressive myelomalacia (PMM).
- Presence and extent of intramedullary T2 hyperintensity,
- T2 hypointensity,
- attenuation of the cerebrospinal fluid (CSF) signal on HASTE/T2* sequences
Minimal sequences to be obtained for IVDD disease MRI?
A minimum of T2W sagittal and transverse images should be acquired.
HASTE and short Tau inversion recovery (STIR), T1-weighted (T1W) and T1W post-contrast sequences might be considered but do not serve as replacements for standard T2W imaging sequences.
Supported by moderate-level evidence.
Benefits of CT over MRI in IVDD?
- rapid acquisition
- lower cost
- better at distinguishing acute from chronic extrusions
- sensitivity 81-100%
Effect of age and size of dogs on CT accuracy for diagnosis of IVDD?
less accurate in:
older (>5 years) and
smaller dogs (<7 kg).
In which canine patients could we reccommend CT as a first line advanced dx imaging modality?
young to middle-aged adult, chondrodystrophic dogs when acute TL-IVDE is suspected –> low likelihood we will miss a lesion, but lower cost/faster acquisition
Reccurence rate for medically vs. surgically treated dogs with IVDD?
15% to 66% compared with much lower rates for dogs managed by both hemilaminectomy and fenestration
Outcomes of dog treated medically vs surgically for IVDD based on severity of presenting signs?
Minimal suggested period of restricted activity in dogs with IVDD treated conservatively?
at least 4 weeks to promote healing of the annulus fibrosus
This period should include confinement to a restricted area (crate ideally, or a small room without furniture) except for when performing rehabilitation exercises or outdoor toileting. There should be no off-leash walking, no jumping on or off furniture and no access to stairs during this time. Supported by low-level evidence.
Effect of durotomy on outcome and PMM in dogs with IVDD?
for dogs with severe neurologic signs may improve outcome and lessen risk of PMM
Fenestration of the herniated disc space at the time of surgical decompression is recommended or not? to minimize risk of recurrence at the site of herniation.
it is reccomended
Rate of reccurence of IVDD for dogs undergoing decompressive surgery?
up to 19%
Which percentage of recurrences of IVDD develop within 1-2 disc spaces of the original extruded disc?
87.5%
Rate of recurrence od IVDD is higher in which breeds of dogs?
dachshunds (25%) and
French bulldogs (44%)
In which dog breeds does the Consensus recommend fenestration even if the discs are not mineralized?
in breeds predisposed to IVDE such as dachshunds and French bulldogs
Reported risks/complications of fenestration?
- extrusion of additional disc into the vertebral canal at the site of extrusion,
- the potential to induce vertebral instability,
- increased morbidity when performed at L5-6 & L6-7,
- pneumothorax
- hemothorax (chemonucleolysis),
- neuromuscular complications secondary to trauma to the peripheral nerve or nerve root,
- hemorrhage from the sinus or vertebral artery,
- development of spondylosis deformans
Overall reported complication rate associated with various fenestration techniques?
low at 0.01%
Fenestration is not recommended for which sites in the dog?
routine fenestration of L4-5 and more caudal sites is not recommended
Caudal to L3-4, fenestration carries increased risk
Fenestration at T10-11 and above usually is not recommended due to the low rate of disc extrusion at these sites.
How long does it take for the void in the annulus fibrosus to heal after fenestration?
4-16 weeks by invasion of fibrocartilage
Percutaneous laser disc ablation (PLDA) is considered a safe and useful method in limiting recurrent disc extrusion, true or false?
true (low - moderate level of evidence ina large number of dogs)
Use of dexamethasone in IVDD in dogs?
Increased risk of urinary tract infection and gastrointestinal disease.
Reduced quality of life in dogs managed medically for IVDE.
Use of dimethyl sulfoxide (DMSO) in dogs with IVDD?
dogs treated with the matrix metalloproteinase (MMP) inhibitor GM6001 with a dimethyl sulfoxide (DMSO) carrier or DMSO alone showed significantly improved locomotor outcome compared to those treated with a saline control.
Which percentage of dogs had persistently increased mechanical sensory thresholds (MST) suggesting neuropathic pain after TL-IVDE?
15%
normally the values stabilise by 6 weeks after hemilaminectomy
Epidural application of morphine or morphine & dexmedetomidine & hydromorphone is associated with better postoperative (48 h) pain control in dogs with IVDD, true or false?
true
Erector spinae block is associated with better postoperative (24 h) pain control in dogs with IVDD, true or false?
true
Fentanyl patch can be considered as a good means of pain control in dogs with IVDD, true or false?
Plasma levels therapeutic, pain control adequate (72 h)
Adjunctive Pregabalin 4 mg/kg q8h post op was associated with better pain control for 5 days post-op in dogs with IVDD, true or false?
true,
1) pregabalin - Better pain control for 5-d postop
2) gabapentin - No benefit over placebo for 5-d postop
Both pre- and postoperative electroacupuncture are associated with reduced pain in dogs undergoing surgery for IVDD?
False
Preoperative acupuncture reduced intraoperative need for fentanyl, reduced pain on recovery from anesthesia.
Postoperative electroacupuncture No benefit for 3-d postop.
Pulsed electromagnetic fields are associated with reduced postop pain in dogs with IVDD?
true, up to 6 weeks
Use of harmonic blade for surgery in dogs with IVDD was associated with reduced postoperative pain?
true, up to 30 days
Minimally invasive surgery was associated with reduced need for opioids and postoperative pain in dogs with IVDD?
true
4 regions of the IVD?
the nucleus pulposus,
the transitional zone,
the annulus fibrosus and the
cartilaginous endplates
Criteria for CT diagnosis of HNPE?
Using contrast-enhancxed-CT, HNPE
was visualised as a hypodense extradural compressive lesion with rim enhancement immediately dorsal
to the intervertebral disc space, with a sensitivity of 91% and a specificity of 100%.
Which percentage of dogs with ANPE show lateralised neuro signs?
90%
(in cats more symmetrical than dogs)
Most common cause of ANPE in cats?
up to 75% of cats with ANNPE present following external trauma
Most common spinal column location of ANPE?
thoracolumbar junction
likely reflecting the increased biomechanical forces at the junction between two stable vertebral segments
MRI criteria for diagnosing ANPE
- Focal intramedullary T2-weighted hyperintensity of the spinal cord
- Spinal cord lesion located overlying an IVD
- Reduced volume of T2-weighted hyperintense nucleus pulposus signal in the affected IVD
- Mild narrowing of the affected IVD in mid-sagittal view
- Small volume extradural material (T2-weighted hyperintense, T1-weighted hypointense) dorsal to the IVD with minimal to no spinal cord compression.
MRI characteristics of Intradural/Intramedullary Intervertebral Disc Extrusion (IIVDE)?
- areas of intramedullary hypointensity on T2-weighted, T1-weighted and gradient echo (T2*) sequences overlying an IVD
- reduced nucleus pulposus volume,
- a linear tract running from the associated IVD to the spinal cord parenchyma
Percentage of dogs with a reduced volume of nucleus pulposus in an adjacent IVD in FCEM?
23.6% - usually the IVD caudal to the intramedullary hyperintensity
Theories how the fobrocartilaginous material gets into the circulation to cause FCEM?
1) Schmorl’s nodes like in humans - herniation of nucleus pulposus into the endplate (but rare in dogs) - lest likely theory
2) directly into the internal vertebral venous plexus or spinal arterial vasculature
3) via new blood vessels forming in annulus fibrosus undergoing age related degenerative changes
4) 2+3
5) Presence of embryonic remnant vessels within the nucleus pulposus (which is normally
avascular in adults)
Percentage of animals where external trauma or exercise is reported prior to FCEM?
30%
Percentage of small breed dogs out of all dogs with FCEM?
24% (1/4)
Most common small-breed dog with reported FCEM?
Miniature Schnauzer (60% of all small breeds)
Breed of dog with very early onset of FCEM (puppy paralysis)?
Irish wolfshound puppies
MRI criteria for FCEM?
- Focal intramedullary T2 hyperintensity, focused on the gray matter and frequently lateralized.
- Spinal cord lesion overlying vertebral body, not IVD.
- No evidence of extradural material in the region of the lesion.
- Subtle reduction in volume of T2-weighted hyperintense nucleus pulposus signal in the disc caudal to the spinal cord lesion.
Classification of SAD?
- Type 1 is extradural without involvement of the nerve,
- Type II is extradural with involvement of the nerve roots,
- Type III is intradural
Most accepted theory of SAD formation?
- the theory of a 1-way valve formed by arachnoid proliferation in which cerebrospinal fluid (CSF) is allowed to flow into the region with pressure changes but cannot flow out
- this supports a congenital etiology despite the range of ages over which clinical signs become apparent as it allows for progressive expansion and therefore, progressive compression of the spinal cord.
Most represented breeds for SAD?
pugs, rottweilers, and French bulldogs,
- Pugs make up 28% (92/324),
- Rottweilers 19% (62/324), and
- French bulldogs 13% (43/324)
Diseases (most commonly) associated/concurrent with SAD in dogs?
- in pugs, caudal articular process dysplasia
- in a recent study in pugs with thoracolumbar SAD, 58% had intervertebral disc disease at the same or adjacent sites
Sex predisposition for SAD?
male sex (ca. 80% of all dogs) (unknown why)
Mean age for developing SAD?
- In a study of 122 dogs, the overall median age of onset of signs was 36 mo and did not vary with diverticulum location.
- However, in a smaller study, SAD dogs in a cervical location were younger with a mean age of 31 mo compared to a mean age of 6.2 y in those with thoracolumbar diverticula.
Incidence for cervical vs. thoracolumbar SAD?
- cervical 41% to 71%
- thoracolumbar 29% to 58%
(depending on the study)
Breed predisposition for different locations of SAD in dogs?
- Pugs, mostly thoracolumbar localization
- French mostly thoracolumbar localization
- Rottweilers cervically located lesions
- In general, dogs with cervical diverticula were significantly larger and dogs with thoracolumbar lesions were more likely to be small breeds
Most common location for a thoracolumbar SAD?
T9–T13
Most SAD lesions are located in the dorsal midline subarachnoid space (XX%-XX%) but they can also occur ventrally, laterally, or in a combination of these surrounding the spinal cord.
83% to 90%
In 1 study of SAD, dogs with bilobed or multilobed lesions were all Rottweilers, and in another study of 10 Rottweilers, all bilobed lesions occurred in a caudal cervical locationm, true or false?
true
Most common neuro sign in dogs with SAD?
- slowly progressive/waxing-waning proprioceptive ataxia was the most common clinical sign in 1 study, present in 92.6% of cases, and
- hypermetria was present in 21.3%.
- Paresis, was much less common, and 50% of the dogs with paresis had concurrent neurologic disease that could have accounted for this finding.
Urinary and fecal incontinence in dogs with SAD are typically attributed to which localisation?
thoracolumbar
Why do some dogs with SAD develop urinary/fecal incontinence?
As lesions are usually located dorsally, fecal incontinence typically occurs secondary to compression of the dorsally located ascending sensory pathways.
Disruption of these pathways interrupts relay of sensory information to the sensory cortex, via the thalamic nuclei, for conscious recognition of rectal distension and defecation.
Incidence of urinary and fecal incontinence in dogs with SAD?
3.3% - 4.1%
Incidence of pain in dogs with SAD?
- variable with 18.9% of dogs showing discomfort.
- however, only 10% were specified to be painful on palpation
- Given that some dogs have concurrent disease, as well as leptomeningeal adhesions, this may play a role in the detection of spinal discomfort.
Magnetic resonance imaging in dogs with SAD is ideal for evaluating the spinal cord parenchyma to find concurrent lesions such as ___________ and _____________.
edema or syringomyelia
and
adhesions
Which MRI sequence, besides sagittal T1W and T2W, can help in the diagnosis of SAD in dogs?
- half-Fourier acquisition single-shot turbo spin-echo pulse sequence (HASTE) in sagittal plane
- it increases the signal intensity of cerebrospinal fluid, while fat has little or no signal so it helps visualize the subarachnoid space and has a relatively short acquisition time
- In a study comparing diagnosis of SAD with T2W imaging alone and HASTE, the sensitivity of T2W alone was 25% compared with the sensitivity of T2W and HASTE at 52.8%. Though not perfect, false negatives were reduced from 75% to 47.2% after the addition of HASTE
Typical CSF findings in dogs with SAD?
- usually normal
- ca. 20% will show non-specific elevations in total protein and 9.2% to 10% have evidence of a mild mononuclear pleocytosis
Role of prednisolone in the treatment of SAD in dogs?
- 26% show improvement on pred
- questionable efficacy prior to surgery
The only study assessing medical management and its outcome as it compares to surgical management is a study of 96 dogs in which 52% of dogs were treated medically, with the treatment of choice being variable courses of prednisone in 44/50 dogs.
Based on recheck visits and owner assessments, over a median follow-up of 24 mo, only 26% showed improvement on prednisone. Anecdotally, corticosteroids are often recommended before surgery, but in a recent study 5 cases in which steroids were used for 2 mo or longer in the perioperative period, showed no association with a better outcome. Whether or not it helps in removing the secondary intramedullary changes observed in the cord (edema, pre-syrinx, syrinx/syringomyelia) is also unknown.
Surgical management has been described with various procedures and approaches including hemilaminectomy, dorsal laminectomy, and ventral slot, based on the location of the diverticulum, combined with some variation of durotomy, durectomy, diverticulum fenestration, dural marsupialization, and vertebral stabilization.
To date, no one procedure is superior and follow-up times are widely variable making assessment of success with each separate procedure difficult to determine. True or false?
true
*but:
Although not statistically significant, 1 study did find a trend towards a better outcome when marsupialization of the dura was performed
Findings showing a trend towards a positive outcome after surgery in dogs with SAD?
- patients younger than 3 y old
- duration of clinical signs less than 4 mo.
A recent study evaluating short- and long-term outcomes following surgery in pugs found that though 82% had a successful short-term post-operative outcome (6 mo), in the long term (12 mo or longer) 86% of pugs showed deterioration with 50% of those undergoing repeat MRI that showed a recurrent SAD or new SAD, true or false?
true
Caudal articular process dysplasia, are present in _______________ % of pugs, and can be found in clinically normal or abnormal dogs.
91.2% to 97%
Which SAD conformation (cranially or caudally thetherd) possibly has a better short-term outcome?
thoracolumbar caudal tethered SAD
Which surgical technique in dogs with SAD can result in mild post-operative deterioration?
closure of the durotomy incision
