Bilateral dangling foot: causes, symptoms, diagnosis

In contrast to unilateral foot drop, which can be of central or peripheral origin, bilateral foot drop always indicates a lesion of the peripheral nerves or muscles. The onset of the disease can be slow, so that the patient gradually gets used to the change in gait, or acute.

I. Chronic:

1. Polyneuropathy.
2. Hereditary motor-sensory polyneuropathy types I and II (Charcot-Marie-Tooth disease).
3. Dystrophic myotonia (Steinert-Batten disease).
4. Myopathy (scapuloperoneal syndrome).
5. Motor neuron disease.

II. Acute:

1. Medial lumbar intervertebral disc herniation.
2. Polyneuropathy.

I. Chronic bilateral foot drop

Polyneuropathy

Chronic development of foot drop is observed in polyneuropathy, especially of metabolic origin, including diabetes mellitus, or toxic origin, including alcohol. Other clinical (subclinical involvement of hands; sensory disturbances) and EMG signs of polyneuropathy are also observed.

Hereditary motor-sensory neuropathy (Charcot-Marie-Tooth disease) is a common cause of chronic, slowly progressing bilateral footdrop syndrome. Its clinical manifestations are quite typical and are often supplemented by a family history. EMG allows to clarify its type.

Dystrophic myotonia (Steinert-Batten disease)

A particularly slow development of foot drop is characteristic of a degenerative muscle disease described by Kurshman and Steinert, and is called dystrophic myotonia or Steinert-Batten disease. The name implies the presence of two components - dystrophic and myotonic - in the clinical picture, which is very characteristic. The unusual gait of these patients is striking. Severe paresis and paralysis of the extensor muscles of the foot are a particular obstacle when the patient tries to turn around. He cannot turn on the heel, as is normal, since this requires lifting the foot, which is impossible for these patients. Instead, they turn slowly, with small steps, always lifting the knees excessively to overcome the drop foot.

On examination, a special habitus is noticeable: the characteristic posture and weak muscles of these patients. Men are usually bald, women have very sparse hair. The face is thin and expressionless (facies myopathica - myopathic face), the corners of the mouth are sometimes lowered ("sad face"). The retina may not be accessible to examination due to cataract of the lens. The dystrophic process especially affects the following muscles: the sternomastoid and brachioradialis muscles, extensors and pronators of the foot. However, dystrophy is widespread, almost all muscles of the face, trunk and limbs are affected. Reflexes are reduced or absent. EMG reveals a myopathic pattern.

The myotonic component is present in patients who complain of an inability to relax quickly after compression. The examination reveals a slow relaxation after a strong compression, which is also the most convenient test for these patients. "Percussion myotonia" can also be assessed by quickly striking the thenar or tongue spatula with a reflex hammer. The response consists of a prolonged contraction that resolves after a period of more than three seconds. The myotonic response is very easily recognized by EMG, when the insertion or any movement of the needle causes a stream of action potentials.

Myopathy

The scapuloperoneal form of myopathy, described by S.N. Davidenkov, is characterized, among other manifestations, by slowly increasing weakness of the peroneal muscles, which leads to the syndrome of chronically progressive bilateral foot drop.

Some forms of amyotrophic lateral sclerosis can also lead to foot drop.

II. Acute bilateral foot drop

Medial lumbar disc herniation

In bilateral foot drop, the diagnostic decision must be quick and effective, as immediate surgical intervention may be necessary. These are the cases where the cause of the extensor paralysis is a medial - as opposed to posterolateral - lumbar intervertebral disc herniation.

The patient may complain of pain in the lumbar region radiating along the flexor side of both legs, reflex tension of the trunk muscles is detected. Achilles reflexes are reduced or absent, Lasegue's sign is positive. Urination is usually blocked. Sensory disturbance (numbness, decreased pain and tactile sensitivity) quickly spreads from the foot, covering both legs. Magnetic resonance imaging should be performed immediately, since in this case there is no real therapeutic alternative to surgical treatment, and the only question is the level of the lesion.

Polyneuropathy

Sometimes, in very rare cases, polyneuropathy leads not only to foot drop, but also to urinary disorders. There is no severe pain or muscle tension in the lumbar region. Electroneurography will not help in diagnosis during the first few days of the disease. In doubtful cases, it should be taken into account that an error can have very serious consequences for the patient. It is better to perform myelography on a patient with polyneuropathy than to miss an acute disc herniation. If the pressure on the equine tail fibers is not immediately relieved, then the consequence of delaying the operation will be only partial recovery or no recovery at all.