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Sensory and Autonomic Disturbances


This chapter deals primarily with sensory disturbances of the limbs and trunk. Autonomic dysfunction is often associated with sensory loss but sometimes occurs alone. Chapter 17 considers sensory disturbances of the face.

Sensory symptoms

Pain, dysesthesias, and loss of sensibility are the important symptoms of disturbed sensation. Peripheral neuropathy is the most common cause of disturbed sensation at any age. As a rule, hereditary neuropathies are more likely to cause loss of sensibility without discomfort, whereas acquired neuropathies are more likely to be painful. Discomfort is more likely than numbness to bring a patient to medical attention.

Nerve root pain generally follows a dermatomal distribution. Ordinarily it is described as deep and aching. The pain is more proximal than distal and may be constant or intermittent. When intermittent, the pain may radiate in a dermatomal distribution. The most common cause of root pain in adults is sciatica associated with lumbar disk disease. Disk disease also occurs in adolescents, usually because of trauma. In children, radiculitis is a more common cause of root pain. Examples of radiculitis are the migratory aching of a limb preceding paralysis in the acute inflammatory demyelinating polyradiculoneuropathy/Guillain-Barré syndrome (see Chapter 7 ), and the radiating pain in a C5 distribution that heralds an idiopathic brachial neuritis (see Chapter 13 ).

Polyneuropathy involving small nerve fibers causes dysesthetic pain. This pain differs from previously experienced discomfort and is described as pins and needles, tingling, or burning. It compares with the abnormal sensation felt when dental anesthesia is wearing off. The discomfort is superficial, distal, and usually symmetric. Dysesthetic pain is almost never a feature of hereditary neuropathies in children.

Loss of sensibility is the sole initial feature in children with sensory neuropathy. Because of the associated clumsiness, delay in establishing a correct diagnosis is common. Strength and tests of cerebellar function are normal and tendon reflexes are absent. The combination of areflexia and clumsiness should suggest a sensory neuropathy.

Table 9.1 summarizes the pattern of sensory loss as a guide to the anatomical site of abnormality and Box 9.1 lists a differential diagnosis of conditions with sensory deficits.

Table 9.1
Patterns of Sensory Loss
Pattern Site
All limbs Spinal cord or peripheral nerve
Both legs Spinal cord or peripheral nerve
Glove-and-stocking Peripheral nerve
Legs and trunk Spinal cord
One arm Plexus
One leg Plexus or spinal cord
Unilateral arm and leg Brain or spinal cord

Box 9.1
Disturbances of Sensation

  • Brachial neuritis

  • Complex regional pain syndrome I (reflex sympathetic dystrophy)

  • Congenital insensitivity (indifference) to pain

    • Lesch-Nyhan syndrome

    • Mental retardation

    • With normal nervous system

  • Foramen magnum tumors

  • Hereditary metabolic neuropathies

    • Acute intermittent porphyria

    • Hereditary tyrosinemia

  • Hereditary sensory and autonomic neuropathy (HSAN)

    • HSAN I (autosomal dominant)

    • HSAN II (autosomal recessive)

    • HSAN III (familial dysautonomia)

    • HSAN IV (with anhidrosis)

  • Lumbar disk herniation

  • Syringomyelia

  • Thalamic syndromes

Painful limb syndromes

Three painful arm syndromes are as follows: acute idiopathic brachial neuritis (also called neuralgic amyotrophy, or brachial plexitis), familial recurrent brachial neuritis, and complex regional pain syndrome (CRPS) (reflex sympathetic dystrophy). In the first two syndromes, muscle atrophy follows a transitory pain in the shoulder or arm. Monoplegia is the prominent feature (see Chapter 13 ). Although muscle atrophy also occurs in CRPS, pain is the prominent feature. Discussion of CRPS follows.

Complex Regional Pain Syndrome I

The presence of regional pain and sensory changes following a noxious event defines complex regional pain syndrome (CRPS). A working group of the International Association for the Study of Pain developed a new terminology that separates reflex sympathetic dystrophy (RSD) from causalgia. CRPS I replaces the term RSD. The definition of CRPS I is defined as “a pain syndrome that develops after an injury, is not limited to the distribution of a single peripheral nerve, and is disproportional to the inciting event.” CRPS II requires demonstrable peripheral nerve injury and replaces the term causalgia. Although CPRS can occur in children and adolescents, it is most common in adults and has a female preponderance. Surgery, minor trauma, and fractures are common inciting events.

Clinical features

The essential feature of CRPS I is sustained burning pain in a limb combined with vasomotor and sudomotor dysfunction, leading to atrophic changes in skin, muscle, and bone following trauma. The pain is of greater severity than that expected for the inciting injury. The mechanism remains a debated issue. Catecholamine hypersensitivity may account for the decreased sympathetic outflow and autonomic features in the affected limb. There is a decrease in C-type and A-delta type fibers in the affected limb, possibly due to imperceptible nerve injury at the time of the inciting event, with a subsequent increase in aberrant nociceptive fibers that are thought to function improperly. The central and peripheral nervous systems demonstrate an enhanced response to pain and perpetuate the symptoms. Genetic and psychological factors likely play a role.

The mean age at onset in children is 11 years, and girls are more often affected than are boys. CRPS I frequently follows trauma to one limb, with or without fracture. The trauma may be relatively minor, and the clinical syndrome is so unusual that a diagnosis of “hysterical” or “malingering” is common. Time until onset after injury is usually within 1 or 2 months, but the average interval from injury to diagnosis is 1 year.

The first symptom is pain at the site of injury, which progresses either proximally or distally without regard for dermatomal distribution or anatomical landmarks. Generalized swelling and vasomotor disturbances of the limb occur in 80% of children. Pain is intense, described as burning or aching, and is out of proportion to the injury. It may be maximally severe at onset or may become progressively worse for 3–6 months. Movement or dependence exacerbates the pain, causing the patient to hold the arm in a position of abduction and internal rotation, as if swaddled to the body. The hand becomes swollen and hyperesthetic and feels warmer than normal.

Children with CRPS I do better than do adults. Reported outcomes vary widely, probably based on the standard of diagnosis. In the author’s experience, most begin recovering within 6–12 months. Long-term pain is unusual, as are the trophic changes of the skin and bones that often occur in adults. Recovery is usually complete, and recurrence is unusual.

Diagnosis

The basis for diagnosis is the clinical features; laboratory tests are not confirmatory. Because the syndrome follows accidental or surgical trauma, litigation is commonplace, and requires careful documentation of the clinical features examination. In recent years, CRPS I has become popular on the Internet and is often self-diagnosed incorrectly by patients with other types of chronic pain syndromes or conversion disorders.

One simple test is to immerse the affected limb in warm water. Wrinkling of the skin of the fingers or toes requires intact sympathetic innervation. The absence of wrinkling is evidence of a lesion in either the central or the peripheral sympathetic pathway. The other unaffected limb serves as a control.

Management

Physical therapy, biofeedback, and counseling are helpful. Nonsteroidal anti-inflammatory drugs (NSAIDs) are standard and may reduce ongoing inflammation. More severe cases may benefit from steroids, gabapentin, or pregabalin. Adrenergic receptor antagonists or alpha-2 receptor agonists (phenoxybenzamine, clonidine) may be useful in managing sympathetically mediated pain. Calcium channel blockade with nifedipine can decrease vasoconstriction. Sympathectomy and spinal cord stimulation, with or without baclofen, can be considered for refractory cases. Emerging treatments include botulinum toxic and immunomodulation; however, additional studies are needed.

Erythromelalgia

Familial erythromelalgia is an autosomal dominant disorder (2q24) caused by a mutation in a gene encoding a voltage-gated sodium channel.

Clinical features

Burning pain occurs in one or more limbs exposed to warm stimuli or exercise. Onset is often in the second decade. Moderate exercise, such as walking, induces burning pain, redness, and warmth of the feet and lower legs.

Diagnosis

The clinical features establish the diagnosis, especially when other family members are affected.

Management

Stopping the exercise provides relief. Sodium channel blockers (carbamazepine, phenytoin, lamotrigine, oxcarbazepine, and possibly lacosamide) are useful to prevent attacks in some families.

Central congenital insensitivity (indifference) to pain

Most children with congenital insensitivity to pain have a hereditary sensory neuropathy. In many early reports, sensory neuropathy was not a consideration and appropriate tests not performed. This section is restricted to those children and families with a central defect. Sensory neuropathy testing is normal and often associated with mild mental retardation. Several affected children are siblings with consanguineous parents. Autosomal recessive inheritance is therefore suspect. The Lesch-Nyhan syndrome is a specific metabolic disorder characterized by self-mutilation and mental retardation without evidence of sensory neuropathy (see Chapter 5 ).

Clinical features

Children with congenital insensitivity to pain come to medical attention when they begin to crawl or walk. Their parents recognize that injuries do not cause crying and that the children fail to learn the potential of injury from experience. The result is repeated bruising, fractures, ulcerations of the fingers and toes, and mutilation of the tongue. Sunburn and frostbite are common.

Examination shows absence of the corneal reflex and insensitivity to pain and temperature, but relative preservation of touch and vibration sensations. Tendon reflexes are present, an important differential point from sensory neuropathy.

Diagnosis

The results of electromyography (EMG), nerve conduction studies, and examination of the cerebrospinal fluid are normal.

Management

No treatment is available for the underlying insensitivity, but the repeated injuries require supportive care. Injuries and recurrent infections reduce longevity.

Foramen magnum tumors

Extramedullary tumors in and around the foramen magnum are known for false localizing signs and for mimicking other disorders, especially syringomyelia and multiple sclerosis. In children, neurofibroma caused by neurofibromatosis is the only tumor found in this location.

Clinical features

The most common initial symptom is unilateral or bilateral dysesthesias of the fingers. Suboccipital or neck pain occurs as well. Ignoring such symptoms is common early in the course. Numbness and tingling usually begin in one hand and then migrate to the other. Dysesthesias in the feet are a late occurrence. Gait disturbances, incoordination of the hands, and bladder disturbances generally follow the sensory symptoms, and are so alarming that they prompt medical consultation.

Many patients have café au lait spots, but few have evidence of subcutaneous neuromas. The distribution of weakness may be one arm, one side, or both legs; 25% of patients have weakness in all limbs. Atrophy of the hands is uncommon. Sensory loss may involve only one segment or may have a “cape” distribution. Diminished pain and temperature sensations are usual and other sensory disturbances may be present. Tendon reflexes are brisk in the arms and legs. Patients with neurofibromatosis may have multiple neurofibromas causing segmental abnormalities in several levels of the spinal cord.

Diagnosis

Magnetic resonance imaging (MRI) is the best method for showing abnormalities at the foramen magnum.

Management

Surgical excision of a C2 root neurofibroma relieves symptoms.

Hereditary neuropathies

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