Deformity of a lower limb

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59 Deformity of a lower limb

Instruction

Examine the lower limbs of this patient who has had this abnormality since childhood.

Diagnosis

This patient has unilateral wasting and deformity of the R/L leg (lesion) caused by poliomyelitis in childhood (aetiology) and wears calipers on that leg (functional status).

Questions

What is the differential diagnosis?

• Old poliomyelitis (Fig. 59.1)

• Spina bifida (Fig. 59.2).

Fig. 59.1 Medial (A) and frontal (B) views and radiograph (C) of severe calcaneocavovarus deformities as sequelae of poliomyelitis.

(With permission from Canale, Beaty 2007.)

Fig. 59.2 Clinical features and corresponding occult spinal dysraphism detected by sagittal, T₁-weighted MRI studies of the spinal cord. (A) Sacral lipoma and deviated gluteal furrow. (B) Lumbar port-wine stain, lipoma, dermal sinus, and deviated gluteal furrow. (C) Dorsal and lumbar unclassified hamartomas. (D) Lipoma of the conus (arrow). (E) Dermal sinus (arrow). (F) Top of the lipoma of the filum terminale (upper arrow) and fistula (lower arrow). (G) Multiple lipomas of the thoracic cord (upper arrow) and posterior conus (lower arrow).

(With permission from Guggisberg et al: 2004.)

What are the causes of lower motor neuron signs in the legs?

• Peripheral neuropathy

• Prolapsed intervertebral disc

• Diabetic amyotrophy

• Poliomyelitis

• Cauda equina lesions

• Motor neuron disease.

Advanced-level questions

What is the cause of polio?

Polio is caused by a picornavirus of the genus Enterovirus; there are three antigenic types: I (Brunhilde), II (Lansing) and III (Leon).

Is the muscular involvement of polio in childhood progressive?

Usually paralytic polio remains stable after the initial attack. However, in some patients new muscle weakness and atrophy involving previously affected muscles or even unaffected muscles occurs and this deterioration can occur as long as 30 years after the first attack; this is known as postpoliomyelitis muscular atrophy (PPMA). The progression of this involvement is slow and is said to be distinct from motor neuron disease. It is not entirely clear why only some patients are affected but it has been reported that it is more likely to occur in those with widespread paralysis and poor immune status (N Engl J Med 1986;314:959).

Is poliomyelitis preventable?

Yes, three types of poliovaccine are available (each containing all three strains of the virus):

• Oral polio vaccine of Sabin consists of live attenuated virus

• Killed or inactivated vaccine of Salk

• Enhanced potency vaccine of van Wezel.

With which vaccine is paralytic poliomyelitis associated?

Vaccine-associated paralytic poliomyelitis (VAPP) is associated with oral polio vaccine, particularly in immunodeficient individuals (N Engl J Med 1995;332:500–6). Such individuals and their household contacts should be given inactivated vaccine.

What do you know about ‘provocation poliomyelitis’?

Provocation poliomyelitis is caused by the administration of intramuscular injections during the incubation period of wild-type poliovirus or shortly after exposure to oral poliovaccine (either as a vaccine recipient or through contact with a recent recipient).

What do you understand by the term spina bifida?

Spina bifida means an incomplete closure of the bony vertebral canal and is commonly associated with a similar anomaly of the spinal cord. The commonest site is the lumbosacral region, but the cervical spine can be involved and may be associated with hydrocephalus. It results from failure of fusion of the caudal neural tube and is one of the most common malformations of human structure. The causes include single gene disorders, chromosome abnormalities and teratogenic exposures. Although the cause is not known in most cases, up to 70% of spina bifida cases can be prevented by maternal periconceptional folic acid supplementation. The mechanism underlying this protective effect is unclear, but it is probably related to genes that regulate folate transport and metabolism. Individuals with spina bifida often require both surgical and medical management. Surgical closure is usually done in the neonatal period. Medical management is a lifelong (Lancet, 2004;364:1885–95).

What are the features of closed spina bifida?

• Cutaneous: lumbosacral lipoma, hypertrichosis, sinus or dimple above the sacrum, naevus or scarring

• Unilateral shortening of one leg and foot with a deficiency of the muscles below the knee. There may be calcaneovalgus or equinovarus deformity. Sensory loss in the fifth lumbar and first sacral dermatome is common

• Neuropathic bladder, enuresis

• Bony changes on radiograph: sacral dysgenesis, scoliosis, laminar fusion of vertebral body, pedicle erosion and bony spurs.

Is the neurological deficit in closed spina bifida progressive?

This issue is contentious as much of the deficit is fixed antenatally and any progression is a result of growth and posture. However, in some patients the late appearance of bladder dysfunction indicates that the neurological deficit is progressive in these individuals.

Mention some teratogenic factors responsible for neural canal defects

• Maternal diabetes and sacral dysgenesis

• Sodium valproate in pregnancy and neural tube defects (Lancet 1982;ii:1282).

Mention some prenatal screening tests for spina bifida

• Amniotic α-fetoprotein levels

• Amniotic acetylcholinesterase estimation

• High-resolution diagnostic ultrasonography.

What is the basic mechanism of muscle atrophy?

Muscle atrophy (associated with disuse, nerve injury, fasting and many diseases including cancer, AIDS and TB) has a single basic mechanism: excessive activation of the ubiquitin–proteasome pathway in the muscle. The proteasome is a large protein complex that acts like a cell’s garbage disposal by grabbing onto excess and damaged proteins and degrading them; ubiquitin is an enzyme (now called ATP-dependent protease) responsible for protein breakdown.

MH Romberg (1795–1873), German neurologist and Professor of Medicine in Berlin.

The 1952 Nobel Prize was jointly awarded to John F Enders (1897–1985), Thomas H Weller (b. 1915) both of Children’s Medical Center and Harvard Medical School, Boston, and Frederick C Robbins (b. 1916) of Western Reserve University, Cleveland, Ohio, for their discovery of the ability of poliomyelitis viruses to grow in cultures of various types of tissue.

US President Franklin Delano Roosevelt is known for his defiant struggle with his permanent lower-limb paresis (caused by polio). In 1937, Roosevelt announced the formation of a National Foundation for Infantile Paralysis that would ‘lead, direct, and unify the fight of every phase of this sickness’. Soon, millions of US citizens were responding to the pleas of the radio personality Eddie Cantor to ‘send their dimes directly to the President at the White House’ and now this movement is called ‘the March of Dimes’.

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