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Achondroplastic dwarfism

Achondroplasia is a type of genetic disorder that is a common cause of dwarfism. People with this condition have short stature, usually reaching a full adult height of around 4'0" (1.2 metres). more...

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Incidence/Prevalence

It occurs at a frequency of about 1 in 20,000 to 1 in 40,000 births.

Clinical features

Clinical features of the disease:

  • dwarfism (nonproportional short stature)
  • shortening of the proximal limbs (termed rhizomelic shortening)
  • short fingers and toes
  • a large head with prominent forehead
  • small midface with a flattened nasal bridge
  • spinal kyphosis (convex curvature) or lordosis (concave curvature)
  • varus (bowleg) or valgus (knock knee) deformities
  • frequently have ear infections (due to Eustachian tube blockages), sleep apnea (which can be central or obstructive), and hydrocephalus

Causes

The disorder is a result of an autosomal dominant mutation in the fibroblast growth factor receptor gene 3 (FGFR3), which causes an abnormality of cartilage formation.

People with achondroplasia have one normal copy of the fibroblast growth factor receptor 3 gene and one mutant copy. Two copies are invariably fatal before or shortly after birth. Only one copy of the gene needs to be present for the disorder to be seen. Thus, a person with achondroplasia has a 50% chance of passing on the gene to their offspring, meaning that 1 in 2 of their children will have achondroplasia. Since two copies are fatal, if two people with achondroplasia have children, there's a 1 in 4 chance of it dying shortly after birth; 2 out of 3 surviving children will have normal achondroplasia. However, in 3 out of 4 cases, people with achondroplasia are born to parents who don't have the condition. This is the result of a new mutation.

New gene mutations are associated with increasing paternal age (over 35 years). Studies have demonstrated that new gene mutations are exclusively inherited from the father and occur during spermatogenesis (as opposed to resulting from a gonadal mosaicism).

For the genetic details: More than 99% of achondroplasia is caused by two different mutations in the fibroblast growth factor receptor 3 (FGFR3). In about 98% of cases, the mutation is a Gly380Arg substitution, resulting from a G to A point mutation at nucleotide 1138 of the FGFR3 gene . About 1% of cases are caused by a G to C point mutation at nucleotide 1138.

There are a couple of other syndromes with a genetic basis similar to achondroplasia, namely hypochondroplasia and thanatophoric dysplasia. Both of these disorders are also caused by a genetic mutation in the FGFR3 gene.

Diagnosis

Achondroplasia can be detected before birth by the use of prenatal ultrasound. A DNA test can be performed before birth to detect homozygosity, where two copies of the mutant gene are inherited, a condition which is lethal and leads to stillbirths.

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Therapeutic exercise as a treatment for lumbar spinal stenosis
From Journal of the American Chiropractic Association, 5/1/02 by Duarte, Manuel

Chiropractic treatments include many possible therapeutic approaches. Chiropractic manipulative therapy, physiological therapeutics, nutrition, orthotics, and therapeutic exercise are all conservative approaches to patient management. As the population continues to age, lumbar spinal stenosis (LSS) is one condition that is being diagnosed with increased frequency.

By definition, LSS is narrowing of the spinal canal, nerve root canal, or intervertebral foramina of the lumbar spine.1 Conservative treatment is advocated in patients with mild to moderate symptoms of LSS, while surgery is reserved for patients with severe symptoms.2 Narrowing may be due to various etiologic factors, such as congenital, metabolic, and degenerative. Narrowing of the spinal canal results in pressure on the spinal cord and/or nerve roots. Degenerative change is the most common cause of LSS.3

Congenital origins of LSS include achondroplastic dwarfism. Acquired conditions (degenerative) include spondylosis, spondylolisthesis, bulging of the intervertebral disc, trauma injury, osteitis deformans, osteoarthritis, and tuberculosis of the spine. Metabolic and endocrine abnormalities, including hypothyroidism, renal osteodystrophy, and acromegaly, are also associated with the development of LSS.4

The most common area of central canal stenosis includes the LAI/L5 region of the lumbosacral spine. The etiology of symptoms is unclear: some authors believe the symptoms are caused by vascular insufficiency of the nerve roots. Other authors consider it to be secondary to mechanical pressure of the spinal cord and nerve roots.5

The pathogenesis of symptoms associated with LSS is thought to be congestion of the microvasculature. This congestion results in ischemia and hypersensitivity of the nerve roots, cauda equina, and posterior root ganglion.6

The most common presenting symptoms of the patient with LSS are sciatica, neurogenic claudication, and low-back pain. Neurogenic claudication is considered to be the classic presenting symptom in patients suffering from LSS. Neurogenic claudication is defined as pain, aching, and cramping connected with paresthesia in the lower limb, associated with walking or exercise in an upright posture.8

Other common presenting symptoms include leg fatigue, abnormal sensation in one or both lower extremities, and fear of falling. The symptoms increase during extension and are relieved with flexion or when seated. Pain is often described as burning or cramping and can be severe. Numbness, tingling, and fatigue are also associated symptoms. The typical patient is more than 50 years old and has a long history of complaints.3

Physical Examination

Physical examination of the patient reveals minimal objective findings. The most common presentation includes a wide base gait, abnormal Romberg test, thigh pain following 30 seconds of lumbar extension, and a variety of neuromuscular deficits.9 Other common findings are decreased spinal extension. Decreased or absent ankle reflexes may be a finding in approximately 50 percent of patients. Objective weakness has been reported to range from 23-51 percent in patients with LSS. Sensory deficits have been found in 51 percent of patients. Positive Straight Leg Raise (SLR) may be found in over half of all patients with LSS.10

The presentation of neurogenic-induced claudication is similar to that of vascular-induced claudication with a few clinically relevant essential differences.

One striking difference is that with neurogenic-induced claudication, the patient must usually sit, lie down, or flex the lumbosacral spine to get relief. Patients walk better going uphill, since this flexes the lumbosacral spine. The patient suffering from arterial insufficiency-induced claudication may usually stand and rest to get relief.

The symptoms of lumbar spinal stenosis may be exacerbated by extension of the lumbosacral spine. Pain may be worse at night and may be exacerbated by coughing.

Lateral spinal stenosis (LSS) may cause symptoms that overlap those of central canal stenosis but also may be consistent with classic radiculopathy. 11 LSS may be caused by spondylolisthesis. With spondylolisthesis there may be neurogenic-induced claudication of one or both legs, burning, aching, or sharp pain following a specific nerve root distribution. Patients often present with a long history of back pain. Unilateral or bilateral leg pain is a predominant symptom and is reported in approximately 90 percent of patients.10

A number of biomechanical factors may contribute to the symptoms in patients with LSS. These factors are the result of long-standing postural imbalances resulting in excessive tone in certain key muscle groups and decreased tone in others. Significant muscle groups are associated with decreased low-back stabilization and include the internal oblique muscles, lumbar extensor group, both the one- and two-joint hip flexors, and gluteus maximus muscles as examples. It is imperative that the doctor of chiropractic examine the appropriate muscle groups for flexibility and strength.

Reduced flexibility of the hip flexor muscles leads to excessive anterior tilt of the pelvis, which results in increased extension of the lumbar spine. Increased extension results in heightened symptoms in the patient with LSS.

The hip extensor muscles are lengthened and placed at a mechanical disadvantage, which leads to early recruitment of the lumbar extensor muscles and also contributes to excessive lumbar extension. 12 The Thomas test is frequently used to evaluate the flexibility of the one- and two-joint hip flexor muscles. The Thomas test requires the patient to lie supine, and the thigh is flexed with the knee bent upon the abdomen. The patient's lumbar spine should normally flatten, or flex. If the spine maintains a lordosis, the test is positive and indicates hip flexion contracture as a result of a shortened iliopsoas muscle.

Manual muscle testing of the hip extensor muscles is important because of the potential imbalance created by tight hip flexors. Tight hip flexors create an inhibition of the gluteus maximus and hamstring muscle group. This inhibition results in muscular weakness.

The strength of the abdominal muscles must also be assessed because weak abdominal muscles contribute to an increased anterior pelvic tilt and a deepening of the lordotic posture.

Diagnosis

The diagnosis must be preceded by a high index of clinical suspicion based on the patient's history and followed by subjective evaluation and physical examination, and finally confirmed by diagnostic modalities.5 Routinely questioning patients about the distance they are able to walk can discern symptoms of neurogenic-induced claudication.

The standard diagnostic modality for confirming the presence of lumbar spinal stenosis is magnetic resonance imaging (MRI).13 Standard lumbosacral radiographs can identify intervertebral disc space narrowing, facet joint hypertrophy, and osteopenic appearance. They are not particularly useful for identifying central canal stenosis or foraminal stenosis.

Computed axial tomography is also occasionally used with contrast and is suggested to have equal sensitivity to MRI. 14 Neurologic testing through nerve conduction velocity testing and electromyogram may be useful for identifying changes associated with lumbar spinal stenosis. Some studies suggest 80 percent of patients with spinal stenosis test positive for nerve conduction velocity testing and electromyogram changes in the presence of severe canal stenosis. Other studies suggest increased findings after activity intense enough to bring about neurogenic-induced claudication (NIC) symptoms.13

Jensen has described a functional test for NIC as being highly accurate. This involves downhill walking in which the patient is asked to maintain a vertical position. The patient must increase the extension of his or her low back, causing "symptom march." Using a treadmill elevated to create a 100 downhill slope can facilitate this. This actively increases subjective symptoms of lumbar spinal stenosis and also increases the likelihood of developing nerve conduction velocity testing and electromyogram changes. 15

Treatment

Management is directed at alleviating symptoms that limit activity and affect quality of life. Patients may be distraught over their inability to walk the way they used to without eliciting the disability and symptomatology associated with LSS.

Generally, the initial approach to management of patients with LSS begins with the most conservative methods available. A conservative approach to therapy may be an acceptable alternative to surgical treatment.

Conservative therapy is the treatment of choice for elderly patients and those with symptoms not severe enough to warrant emergency surgical intervention.2 Symptoms that would alert the doctor to a severe presentation of LSS might include the diagnosis of cauda equina syndrome. A delay in the diagnosis and treatment of cauda equina syndrome has been shown to increase the risk of permanent neurologic damage.8

The signs and symptoms of cauda equina syndrome are listed at right in Table 2:

Exercise, weight reduction, orthotic devices, physiologic therapeutics, and chiropractic manipulative care may be part of a conservative treatment approach.

In 1985, manipulative therapy was found by Kirkaldy-Willis to improve symptoms in 36 percent of LSS patients who received manipulation. DuPriest mentions a case study where flexion-distraction manipulation was used with exercise, heel lifts, massage, and ultrasound to the patient's benefit.16 Chiropractic manipulation was found by Foreman (Nagler/Hausen) to reduce local ischemia and mechanical compression to chronically irritated nerve roots.17

Surgical intervention is reserved for those patients who experience intolerable pain, progressive neurologic deficits, cauda equina syndrome, or who fail to respond to conservative measures.

DuPriest suggests the following criteria for appropriate chiropractic treatment programs:

Symptoms are posture dependent.

Segmental instability is absent.

The patient is cognitively and physically able to participate in the requirement of the treatment program.

Conservative treatment seems to be a natural choice when symptoms are mild. Although inferior to surgery for the long-term relief of symptoms, conservative treatment proves appropriate for approximately one-half of the patients with mild symptoms.

Guidelines for handling patients with symptomatic lumbar spinal stenosis include:

When pain is moderate, conservative treatment will give a satisfactory result for one-half of the patients in less than three months.

Patients with severe pain and those in whom a conservative approach does not give a satisfactory result should be offered surgical treatment.

Amundsen followed 100 patients with LSS who were given either surgical or conservative treatment for 10 years. He found if pain was moderate, conservative treatment will give a satisfactory result for one-half of the patients in less than three months. Patients with severe pain and those in whom a conservative approach does not give a satisfactory result should be offered surgical treatment More than one-half of the conservatively treated patients had a satisfactory outcome, and a delay of surgery for some months did not worsen the prognosis. He concluded a primarily conservative approach is recommended.18

Therapeutic Exercise

Therapeutic exercise is one of the conservative treatments recommended for patients with LSS.

Several authors advocate the use of flexion exercises exclusively because the spinal canal and neuroforamina narrow as a result of lumbar extension.19

A therapeutic exercise program should be tailored to each individual patient and should accommodate limitations imposed by other existing medical problems. A positive history of cardiovascular or pulmonary disease and obesity may require other concurrent care before beginning a therapeutic exercise program.

The therapeutic exercise program should take into consider ation fitness, stamina, flexibility, strength, power, and postural education.

A goal of an exercise program is to decrease the extension forces on the lumbar spine. These forces are attributable to agonist muscle tightness, antagonist weakness, or both. The therapeutic result is a decrease in the lumbar lordosis.

The use of treadmills, bicycles, and aquatic programs may be used to attain the goals of exercise. Education in proper posture and efficient body mechanics during daily functional activities is essential to maintain the gains made through the therapeutic exercise program.

The program should begin with a general warm-up consisting of either treadmill or bicycle riding, followed by longduration stretches that favor more permanent muscle elongation.20

Fig. 1 Illustrates a stretch of hip flexors. A modification of the hip flexor stretch can be performed as demonstrated in Fig. 2 and Fig. 3. The patient is instructed to hold the stretch for 15-30 seconds and repeat 2 times as tolerated. These exercises could be performed twice daily. Throughout the exercise, the pelvis should maintain a neutral or a slight posterior tilt.

A stretch of the hamstring muscles is illustrated in Fig. 4. The lumbar paraspinal muscles can be stretched while the patient is in a supine position (see Fig. 5).

The abdominals can be exercised using an oblique crunch with arms crossed (see Fig. 6). The patient is instructed to perform two to 3 sets of 15 to 20 reps, with a 4- to 10-second hold once daily.

Bridging is an exercise used primarily for gluteal strengthening (see Fig. 7). This exercise is performed for 2 to 3 sets of 15 to 20 reps with a 4- to 10-second hold once daily.

Therapeutic exercise should be performed at home on a daily basis initially, and at least every other day thereafter. Precautions are given to discontinue any prescribed exercise that leads to recurrent symptoms. Periodic re-evaluation can be used to modify or advance the exercise program as appropriate. Therapeutic exercise is one of many conservative treatments for patients with LSS. The goal of these treatments is to decrease symptoms and increase function by decreasing lumbar lordosis, thereby increasing lumbar flexion.

Referenced

1. Bodack PM, Monteiro M Therapeutic excercisein the treatment of patients with &mbar spinal stenosis.Clinical:al Orthopedica and Related Research, Nunber384pp.144-152, 2001.

2. Bridwell Kf. Lumbar spinal stenosis diagnosis: management and treatment. Clip Geriatr Med 1994;10..677-710.

3. Snow G. Chiropractic management of a patient with lumbar spinal stenosis. Journal of Nanp and PhysiolTher, May 2001;24(4).

4. Nagle W, Hausen H Conservative management of lumbar spinal stenosis. Postgraduate Medicine, April ]998;103(4). 5. Goldman S, Funk J, Christensen M. Spinal steno, Common Cause Podiatric Symptoms, March 1997,-87(3)3.

6. Alvarez J, Hardy R Jr. Lumbar spine stenosis; a common cause of back and leg pain. Am Fam Physican 1998;57.182534,1839-40.

7. Amundsen T Weber H, Li&ae F et aL Lumbar spinal stenosis: Clinical and radialogic features. Spine 20:1178-1186, 1995.

8. Onel D, Hidayet S, Cigdem D. Lumbar spinal stenosis: clinicalradiologic therapeutic evaluation of 145 patents. Conservative treatment or surgical intervention? Spine 1993;18.291-8.

9. Katz J, Dalgas M, Stucki G, Katz N, Bayley J, Fossel A, et at Degenerative lumbar spine stenosis. Diagnostic value of the history ana physical examination;gn. Arthritis Rheum

1995;38:1236-41.

10. Turner J, Ersek M, Herron L, et aL Surgery for lumbar spinal stenosis: attempted meta-analysis of the literature. Spine 17.1-8,1992.

11. Ellenberg M, Reina N, Ross M, et al Regression of herniated nucleus pulposus: two patients with lumbar radiculopathy. Arch Phys Med Rehabil 1989;70: 842.

12. Weintein S, Herring S. Rehabilitation of the patient with low back pain. In DeLia J, Gang B (eds). Rehabilitation Medicine: Principles and Practice. Ed 2. Philadelphia, JB Lippincott, 1993; 996-1017.

13. Haughton V Nondcogenic lumbar radiculopathy: imaging consideration. Sem Ultrasound CT MR 1993;14. 414.

14. Ross J, Modic M Current assessment of spinal degenerative disease with magnetic resonance imaging. Clin Orthop

1992; 279, 68.

15 Jen.4en 0, Schmidt-Olsen S. A new functional test in the diagnostic evaluation of neurogenic intermittent claudication. Clin Rheumatol 1989; 8, 565.

16. DuPriest C. Nonoperative management of lumbar spinal stenosis. J Manip Physiol Ther 1993;16,411-4.

17. Foreman S. Nerve root ischemia and pain secondary to spinal stenosis syndrome: techncial and clinical consideratons. J Manip Physiol Ther 1985;8,81-5.

18. Amundsen T, Weber H, Nordal J Lumbar dpt`nal stenosis: Conservative or surgical management, Spine 2000; 25(11)1424-1456.

19. Fast A. Low back disorders: Conservative management. Arch Phys Med Rehabil 1998;69(10):880-91.

20. Joynt RL, Findley T, Boda W, et al. Therapeutic exercise. In DeLia J, Gans B (eds). Rehabilitation Medicine: Principles and Practice. Ed 2. Philadelphia, JB Lippicott, 1993; 526-554.

By Dum, MS, DC, DABCO

Dr. Manuel Duarte is a professor at National University of Health Sciences. He has taught in the department of chiropractic practice, and is currently senior staff clinncian, and clinic director. Dr. Duarte is a featured speaker in Foot Levelers' license renewal seminar series.

Copyright American Chiropractic Association May 2002
Provided by ProQuest Information and Learning Company. All rights Reserved

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