anatomical variations associated with the vertebral column Flashcards
(151 cards)
1
Q
Sclerotome parts of the somites formed from what?
A
mesodermfrom the vertebrae.
2
Q
during week 4 what happens to the sclerotome?
A
the sclerotome migrate around the neural tube and notochord descending cranial to caudal.
3
Q
The sclerotome undergoes what?
A
resegmentation which is when the caudal half fuses with the cephalic half of the subadjacent sclerotome.
4
Q
mesenchymal cells do what?
A
Mesenchymal cells fill the space between the sclerotomes but they do not proliferate and they contribute to the intervertebral discs.
5
Q
The notochord remains as what?
A
The notochord remains as the nucleus pulposus but is not present in vertebral bodies.
6
Q
Myotomes bridge what?
A
Myotomes bridge the intervertebral discs and this allows movement of the vertebral column.
7
Q
Chondrification centres where and when?
A
form within the sclerotome mesenchyme at week 6 and cartilage replaces it.
8
Q
During week 8 what occurs?
A
cartilage is replaced by bone with 3 primary ossification centres. One centre in the endochondral centrum which will become the vertebral body and the other perichondral centres in each half of the neural arch.
9
Q
what is the last region to ossify?
A
spinous process
10
Q
Regional differences caused by what
A
expression of the HOX gene.
11
Q
is congenital absence of the posterior arch of the atlas rare?
A
yes
12
Q
do congenital absence of the posterior arch have symptoms?
A
asymptomatic mostly
13
Q
what are some of the symptoms of congenital absence of the posterior arch?
A
from mild neck pain to neurological deficits after traumatic injury.
14
Q
what can congenital absence of the posterior arch be associated with?
A
occipitalisation of the atlas or block vertebra.
15
Q
what is type a of congenital absence of the posterior arch?
A
failure of posterior midline fusion
16
Q
what is type B of congenital absence of the posterior arch?
A
unilateral defect
17
Q
what is type C of congenital absence of the posterior arch?
A
bilateral defect
18
Q
what is type D of congenital absence of the posterior arch?
A
absence of posterior arch with preservation of posterior tubercle
19
Q
what is type E of congenital absence of the posterior arch?
A
absence of posterior arch including tubercle
20
Q
what is the Arcuate foramen?
A
is an extra bony feature present on the posterior arch of the atlas.
21
Q
what results in the Arcuate foramen?
A
A result of ossification of the lateral edge of the posterior atlanto-occipital membrane.
22
Q
what can the arcuate foramen cause?
A
May lead to compression of the vertebral artery.
23
Q
what are the ways to classify the arcuate foramen?
A
Partial or complete ossification
Bilateral or unilateral
24
Q
what is common for the arcuate foramen to co-exist with?
A
Common to co-exist with stretching of the vertebral artery on rotation at C1-2 level.
25
The artery passing through the arcuate foramen on the opposite side to the direction of head turn becomes what?
becomes elongated and narrowed compressing against the lateral mass of the atlas – impairing blood flow
26
implications of arcuate foramen compression of neurvascular structures?
```
Barre Lieou syndrome
Vertebrobasilar ischemia
Vertigo
Headaches
Neck pain
Vertebral artery strokes
Vision disturbance
Hearing loss
Neuralgia
Loss of consciousness
Thrombus
Dissection
```
27
The ventromedial portion of the somite forms what?
sclerotome which surrounds the notochord and develops
| into the vertebral body.
28
The dorsal portion surrounds what?
the neural tube and develops into the posterior
| vertebral arch
29
The caudal half of each sclerotome combines with what?
with the cranial half of the sclerotome
| below it.
30
The cranial half of the first cervical sclerotome combines with what to form what?
with the caudal half of the last
| occipital sclerotome to form the base of the skull,
31
the caudal half of the first cervical sclerotome
| combines with what?
with the cranial half of the second cervical sclerotome to form the first cervical vertebra, the
pattern continues in this fashion to form the rest of vertebrae.
32
```
The body, posterior arch and transverse processes of second
cervical vertebra (axis) is derived from what?
```
from second cervical sclerotome
33
what is Occipitalisation of Atlas?
Congenital fusion of the atlas and the occiput
34
how often does Occipitalisation of Atlas occur?
0.08%-3%
35
what are the causes of Occipitalisation of Atlas?
Failure of segmentation - Possibly to do with inactivation of HOX D-3
36
what are the fusion types of Occipitalisation of Atlas?
- Complete fusion: anterior arch, lateral masses and posterior arch
- partial fusion: osseous discontinuity between occiput and part of the atlas
37
what are the classifications of Occipitalisation of Atlas?
Zone 1: anterior arch
Zone 2: lateral processes Zone 3: posterior arch
Combinations of zones
38
what is Neurological compression syndrome due to?
due to the proximity to the spinomedullary region – narrows the foramen magnum which may compress the brain stem, vertebral artery and cranial nerves
39
what are some of the associated cranial nerve problems?
tinnitus, visual disturbances lower cranial nerve palsies leading to dysphagia and dysarthria
40
what is Subluxation?
ligamentous laxity and instability with ageing
41
how common is spina bifida of the atlas?
3% of normal adults
42
is the Accessory Ossicle of the Anterior Arch of the Atlas rare or very common ?
rare
43
is Accessory Ossicle of the Anterior Arch of the Atlas pathological?
no, normal anatomical variant
44
what are the implications of Accessory Ossicle of the Anterior Arch of the Atlas
- Interference with rotatory movements
- Degenerative changes
- Neck pain
45
what is the most common type of accessory rib?
lumbar rib
46
development of costal processes usually on seen where?
thoracic region
47
lumbar rib is usually symptomatic or asymptomatic?
asymptomatic
48
lumbar rib is associated with what?
lumbarisation
49
variations of the cervical rib is how common?
0.5% of population with 10% symptomatic
50
is cervical rib variations more common in females or males?
females
51
what percentage of cervical rib variations is bilateral?
50-80%
52
symptoms for cervical rib variation is usually what?
neurological but sometimes arterial
53
what usually occurs to the cervical rib in variations?
C7 costal element which is usually a small part of the transverse process becomes abnormally large
54
the extra rib or fibrous connection extends where\?
extends to the thoracic rib and may put pressure on the superior thoracic aperture leading to thoracic outlet syndrome
55
thoracic outlet syndrome is caused by what?
Caused by compression of the neurovascular bundle extending from the upper thorax to the axilla
56
the compression in relation to the thoracic outlet syndrome can be caused by what?
caused by the cervical rib, bony tubercles, thoracic rib or soft tissuestructures
57
what is the most common lumbosacral transitional anomalies?
sacralisation of L5
58
lumbrosacral junction in relation to sacralisation of L5 is where?
L4-S1
59
what is present in relation to lumborisation of S1?
S1 displays a lumbar vertebrae configuration
60
lumbrosacral junction in relation to lumborisation of S1 is where?
L6-S1
61
what is Type I?
Dysplastic transverse process, Unilateral or bilateral large triangular transverse process, at least 19 mm wide
62
what is Type II?
Incomplete lumbarisation / sacralisation, Enlarged transverse process with unilateral or bilateral pseudarthrosis with the adjacent sacral ala
63
what is Type III?
Complete lumbarisation / sacralisation, Enlarged transverse process, with unilateral or bilateral complete fusion with the adjacent sacral ala
64
what is Type IV?
mixed, Type II on one side and type III on the other
65
what is held responsible for
| the segmental development of the lumbosacral?
Genetic factors
66
During embryogenesis, the axial skeleton
| is derived from what?
the paraxial mesenchyma that
| surrounds the neural tube.
67
The mesenchyma undergoes what?
craniocaudal segmentation, resulting in clusters
| of cells, the so-called somites
68
The somites
| are segmentally organised in what?
pairs on both sides of
the neural tube and are specific for the axial level at
which they are positioned
69
This segmental
| identity of the somites is determined by what?
different
| Hox-genes in the presomitic mesoderm
70
what are the implications of lumbrosacral transitional anomlies?
```
Backache
Intervertebral disc herniation
Intervertebral disc degeneration
Facet joint arthrosis
Spinal canal stenosis
Lumbar scoliosis
Lumbar extradural defects
Spondylolisthesis
```
71
what is spina bifida?
Vertebral column is open due to failure of fusion of neural arch
72
in spina bifida when does the neural tube not close?
4th week
73
what happens to the neural arch in spina bifida?
Neural arch halves fail to fuse to form the vertebral arch
74
what are the 2 types of spina bifida?
spina bifida occulta or spina bifida cystica
75
what are the incidence levels of spina bifida?
1 in 1000 births
76
is spina bifida more common in males or females?
females
77
what is spina bifida occulta?
covered by a thick membrane or skin
78
what is spina bifida cystica?
open with a thin membranous layer
79
what is meningocele?
can be both open and closed with spinal cord within the canal
80
what is myelomeningocele?
severe open for with spinal cord lying out with the spinal canal
81
is spina bifida occulta usually symptomatic or asymptomatic?
usually asymptomatic
82
what is spina bifida occulta associated with?
with skin abnormalities or tethered cord
83
some symptoms of spina bifida occulta?
pain, weakness, incontinence
84
spina bifida cystica involves what?
spinal cord and the meninges
85
in spina bifida cystica neurological deficits below what?
below the point of lesion
86
chiari type II is what?
hindbrain malformation, venticulomegaly, hydrocephalus
87
what is butterfly vertebrae?
Rare congenital abnormality Symmetric fusion defect
88
when does butterfly vertebrae occur?
3-6 weeks
89
what occurs in butterfly vertebrae?
Sagittal cleft due to persistence of notochord
| Failure of both chondrification centres to fuse in the midline results in butterfly vertebrae
90
associations of butterfly vertebrae?
```
Kyphoscoliosis
Hemi-vertebrae
Spina Bifida
Diastematomyelia
Supernumerary lumbar vertebrae
Congenital syndromes (Pfeiffer, Jarcho-Levins, Crouzon or Alagille syndrome)
Chromosomal defects (22q11 deletion)
```
91
what is hemivertebra?
a rare congenital malformation of the spine where only one half of the vertebral body develops.
92
when occurs during the early development in relation to hemivertebra?
During very early development, the notochord and developing neural tube become surrounded by a mesenchymal template.
93
what happens during week 6 in relation to hemivertebra?
as many as 6 chondrification centres appear in the mesenchymal template, including one centre for each lateral half of the centrum.
94
what happens during week 8 in relation to hemivertebra?
These lateral chondrification centres will fuse by the 8th week to form the single ossification centre of the centrum.
95
is cartilage vascular or avascular?
avascular
96
If one of the chondrification centres fails to develop what occurs?
only half of the vertebral body develops which is wedge-shaped and results in congenital scoliosis.
97
The incidence of hemivertebra is estimated at what?
to be 0.5-1.0 cases per 1000 births, and is more prevalent in females.
98
It has been proposed that hemivertebra results from what?
an abnormal distribution of intersegmental arteries in the developing vertebral column
99
hemivertebra is commonly associated with what?
other anomalies of the spine and limbs.
100
what is block vertebra?
Is the partial or complete fusion of adjacent vertebral bodies.
101
when does block vertebra occur?
Occurs when segmentation of the sclerotomes fails to occur correctly during development.
102
the fused vertebra in relation to block vertebra do what?
The fused vertebrae behave structurally and functionally as one unit.
103
where is block vertebra most common?
cervical and lumbar regions.
104
incidence rates of block vertebra?
Very rare. The most common fusion occurs in 0.4% of births, and is not more common in a particular sex.
105
is block vertebra symptomatic or asymptomatic?
Usually asymptomatic until early adulthood.
106
how else can block vertebra be acquired?
following infection, juvenile arthritis and trauma.
107
symptoms of block vertebra?
decreased range of movement and muscular atrophy.
108
Block vertebra results in what?
greater biomechanical stress in the adjacent vertebrae, particularly the inferior vertebra. This leads to premature degenerative changes of the vertebral body and the intervertebral disc, including intervertebral disc tear and decreased vertebral body height.
109
Unlike the other cervical vertebrae, the C7 vertebra usually has what?
a single, long monofid (non-bifurcated) spinous process.
110
In a study Cho et al. (2012), C7 was what?
Monofid in 95.9% of cases,
Partially bifid in 3.9% of cases, and
Bifid in 0.2% of cases.
111
what is spinous process deviation?
The movement of the spinous process away from the midsagittal line.
112
spinous process deviation is most common in which vertebrae?
lumbar
113
spinous process deviation is associated with what?
May be associated with rotation of the vertebra around its longitudinal axis, or asymmetrical development of the vertebral arch.
114
another potential cause of spinous process deviation is what?
is asymmetrical loading and muscle growth.
115
A clinical trial found what in relation to spinous process deviation?
that patients with spinous process deviation had unequal muscle fibre lengths.
116
spinous process deviation is commonly associated with what?
Intervertebral disc prolapse,
Lumbar stenosis, and
Degenerative spondylolisthesis.
117
The odontoid process, or dens, develops from what?
two primary ossification centres at the superior margin of the developing anterior body of C2. These are partially ossified and are fused in the midline by birth.
118
The dens fuses with the anterior body and the neural arches when?
between 3 and 6 years of age.
119
what is os odontoideum?
The formation of a bony fragment due to unsuccessful fusion of the odontoid process and the vertebral body of C2.
120
what does os odontoideum result in?
in instability and reduced joint mobility at the atlantoaxial joint.
121
once os odontoideum is diagnosed what happens?
it must be treated as migration of the bony fragment can compress the spinal nerves and cause compression of the spinal cord and canal at C1
122
is os odontoideum rare or common
very rare
123
The ossiculum terminale develops from what?
a single ossification centre and is the final part of C2 to fuse
124
in 80% of cases, it fuses to the rest of the odontoid process between when?
8.2 and 10.5 years.
125
A persistent ossiculum terminale occurs when what?
the ossiculum terminale fails to fuse to the odontoid process.
126
what is Persistent Ossiculum Terminale?
It is an incidental finding, often mimicking a Type I dens fracture.
127
how can Persistent Ossiculum Terminale be distinguished?
by a V-shaped cartilaginous cleft between the ossiculum terminale and the odontoid process.
128
is Persistent Ossiculum Terminale symptomatic or asymptomatic?
asymptomatic
129
sesamoid ossicles are what and develop where?
Sesamoid ossicles are small, usually rounded bones which develop within tendons and sometimes ligaments.
130
sesamoid ossicles within the nuchal ligament are usually discovered how?
incidentally during lateral radiographs of the cervical region.
131
what is the cause of sesamoid ossicles?
Their cause is unknown, although it is thought that repetitive injury and irritation over a period of time causes metaplasia of the connective tissue into bone.
132
Routine spinal X-rays have revealed what in relation to sesamoid ossicles?
some degree of calcification of the nuchal ligament in 18% of the general population.
133
incidence level of sesamoid ossicles?
is 2-3 times greater in males than in females.
134
Sesamoid ossicles in the nuchal ligament are most frequent when?
after the third decade of life, with the greatest incidence between 50 and 60 years of age.
135
In more than 75% of cases, the ossicles are found where?
at the C4-5 and C5-6 vertebral levels.
136
The formation of the ossicles is usually accompanied by what?
chronic pain in the cervical region and decreased range of movement of the neck.
137
how is sesamoid ossicles treated?
Is usually treated with anti-inflammatory drugs and shockwave therapy.
138
Surgical excision is never an option in relation to sesamoid ossicles due to what?
as damage to the nuchal ligament can result in cervical spine instability.
139
During development, the neural arches develop from what?
primary ossification centres.
140
The inferior articular facets then develop from what?
secondary ossification centres and fuse with the neural arches.
141
If fusion fails to occur what happens in relation to the oppenheimer's ossicles?
the inferior articular facets exist as separate bony fragments called Oppenheimer’s ossicles.
142
In 80% of cases, the ossicles in relation to oppenheimer's ossicles are what?
are bilateral.
143
when the oppenheimer's ossicles are bilateral where does this occur?
This occurs most frequently in the lumbar region, specifically L2 and L3.
144
where is oppenheimer's ossicles most common?
Is 6 times more prevalent in males than in females
145
where is oppenheimer's ossicles found?
incidentally when scanning the back for other conditions.
146
It is important to distinguish Oppenheimer’s ossicles from what?
from inferior articular process fractures, especially if the scan was for traumatic injury.
147
what is Oppenheimer’s ossicles associated with?
with lower back pain due to compression of the spinal cord.
148
what is duplicated transverse process?
This is an extremely rare anatomical variation, with only 1 reported case in the literature.
149
what was found in the case study for duplicated transverse process?
A single T10 vertebra was found to have 2 transverse processes on the left side.
150
what happened within the case study for duplicated transverse process?
The specimen was isolated, but both transverse processes had articular facets and therefore the authors believed they would have articulated with ribs during life.
151
aetiology of duplicated transverse process?
aetiology is also unknown, although the authors suggested it may be associated with chromosomal translocations or notochord development.
