Charu Gauba, Mukul Verma, Vinit Suri, and Pooja Chopra

A 50-year-old male patient was admitted to hospital with a history of rapidly ascending paraparesis for the past 6 days followed by difficulty in breathing. He had an episode of acute gastroenteritis 2 weeks prior to the onset of the illness. His deep tendon reflexes were absent. Cerebrospinal fluid (CSF) examination showed raised protein with normal sugars and normal cell count.

Patients with rapid onset of flaccid paralysis pose a diagnostic and therapeutic challenge to the treating clinician. Systematic assessment, constructing a differential diagnosis, and rational approach to this problem will help in preventing intercurrent complication of this condition.

Step 1: Assess the patient

•Initiate resuscitation (see Chap. 78).

•Acute weakness may directly lead to admission to the ICU (Table 29.1) or may occur during an episode of critical illness.

•Immediate assessment of the patient’s clinical condition and the duration of symptoms are the most important factors for determining the need for ICU care.

•Airway and breathing should be assessed for the need for airway protection and ventilatory support (Tables 29.2 and 29.3).

•Assess circulation by pulse rate, pulse volume, and blood pressure. If tachycardia is present or BP is low, IV fluid bolus should be given.

C. Gauba, M.D., D.N.B. (*) • M. Verma, M.D., D.M. • V. Suri, M.D., D.M. Department of Neurology, Indraprastha Apollo Hospitals, New Delhi, India e-mail: charugauba@hotmail.com

P. Chopra, M.D.

Department of Respiratory & Critical Care Medicine, Indraprastha Apollo Hospitals, New Delhi, India

Table 29.1 Causes of admission to the ICU

Inability to cough out secretions

Inability to swallow and at risk of aspirating orogastric secretions

Impaired respiratory muscle function leading to respiratory failure

Secondary complications of primary disease—sepsis

Table 29.2 Clinical criteria that point toward respiratory failure

Tachypnea, variable respiratory pattern, paradoxical abdominal breathing, with alveolar hypoventilation and carbon dioxide retention

Dyspnea might not be a predominant symptom in patients with respiratory failure due to neuromuscular weakness

Impaired forced expiration results in ineffective cough causing accumulation of secretions

Retention of secretions results in segmental collapse and ventilation perfusion mismatch

Table 29.3 Bedside procedures that indicate requirement of intubation

Inability to count till 20 in a single breath

Forced vital capacity of less than 15 mL/kg

Negative inspiratory pressure of less than 25–30 cm H2O

Arterial PO2 of less than 70 mmHg on room air

Dysphagia with bulbar muscle involvement

Step 2: Neurologic assessment

•Detailed history about presenting complaints, preceding illness, immunization, or other comorbidities should be taken from the patient and the family.

•Detailed examination helps in pointing toward a diagnosis. Specific therapy may then be given.

•The first step is to decide whether it is an upper motor neuron or lower motor neuron lesion. Further anatomic localization along the neuraxis can then be done depending on the specific features.

–Upper motor neuron diseases may be caused by lesions in the brain or spinal cord.

–Upper motor neuron weakness has a pyramidal distribution with greater involvement of extensors in upper limbs and flexors in lower limbs. Spasticity, brisk reflexes, clonus, and extensor plantars with usually no muscle wasting are seen.

–In the acute stage of a cerebral or spinal insult, patients may present with flaccid weakness and areflexia. This is called cerebral or spinal shock; typical upper motor neuron signs develop later in the illness. Differentiation from lower motor neuron causes of weakness may be done by noting the associated features.

•Altered sensorium, seizures, hemiparesis unless bilateral involvement— cerebral lesions

•Craniopathies with crossed hemiparesis—brainstem lesions

•Root pains, girdle sensation, sensory level over the trunk, bladder involve- ment—spinal cord lesions

–Lower motor neuron diseases may be caused by lesions in the anterior horn cells, roots, plexus, nerves, neuromuscular junction, or muscles (Table 29.4).

–Wasting, fasciculations, hypotonia, and diminished or absent reflexes may be seen in lower motor neuron diseases.

–In anterior horn cell disease, weakness and wasting may be patchy, muscle fasciculations are present, and there is no sensory involvement.

–Root or plexus lesions are painful and asymmetrical, involving the corresponding myotomes or dermatomes.

–In lesions of peripheral nerves, there is symmetrical, usually distal, weakness with glove and stocking sensory loss and distal reflexes are absent. In Guillain– Barré syndrome (GBS), however, proximal weakness is often found and sensory symptoms may be present though without any sensory signs.

–In diseases of the neuromuscular junction, there is history of true fatigability. Ptosis, eye movement abnormalities, faciobulbar weakness, proximal limb weakness, and absence of sensory involvement are the characteristic abnormalities.

–In myopathies, there is symmetrical, usually proximal, muscle weakness and deep tendon reflexes are present unless there is severe muscle wasting and there is no sensory loss.

•Neuromuscular pathology in the critically ill patient develops in two settings: primary neurological diseases that require admission to the ICU for close monitoring or mechanical ventilation, and peripheral nervous system manifestations secondary to critical systemic diseases.

•The most frequent conditions in the first group are GBS, myasthenia gravis, and anterior horn cell disease, and in the second group, critical illness polyneuropathy and myopathy.

•The presenting picture is different since the former group includes acute pathologies that motivate ICU admission, whereas the latter group comprises polyneuropathy or myopathy acquired during hospitalization.

•Of the above illnesses, GBS and critical illness neuropathy/myopathy may be difficult to differentiate from each other. Involvement of the facial and bulbar muscles and autonomic nervous system along with CSF albuminocytologic dissociation is common in GBS, which does not occur in critical illness polyneuropathy.

•GBS is typically an acute demyelinating neuropathy though axonal variants also occur. Critical illness neuropathy, on the other hand, is of the axonal type.

•The functional prognosis of primary muscle impairment tends to be quite good, but both critical illness polyneuropathy and myopathy resolve very slowly over weeks or months with the possibility of a significant residual deficit after 2 years in the most severe cases.

Step 3: Send investigations

•Blood tests

1.Serum potassium, calcium, and creatine phosphokinase are required when muscle pathology is suspected.

2.Blood sugar levels, renal and liver function tests, vitamin B12 levels, and serum protein electrophoresis should be tested in diseases of the peripheral nerves.

3.Thyroid function tests and vasculitic markers are useful in the case of both neuropathies and myopathies.

4.Anti-acetylcholine receptor antibodies are a sensitive test for diagnosis of myasthenia gravis.

•Imaging: It is required in suspected CNS disease.

•Electromyogram (EMG) and nerve conduction velocity (NCV) studies are required to diagnose nerve and muscle disease.

1.In demyelinating neuropathy, distal latencies are prolonged with dispersed compound muscle action potentials (CMAP). There may be conduction block, and nerve conduction velocity may be decreased on nerve conduction studies.

2.In axonal neuropathy, there is decrease in amplitude of action potential on nerve conduction studies. EMG shows spontaneous activity in the form of fibrillation potentials and positive sharp waves with decreased recruitment.

3.In myopathies, small-amplitude, short-duration, polyphasic action potentials are seen on EMG with rapid recruitment.

•CSF examination: Albuminocytologic dissociation (increased protein with normal cell count) is seen in GBS. On the other hand, high protein levels with pleocytosis and normal or low sugars are seen in infectious diseases.

•Spirometry: It is required for the measurement of vital capacity and peak flow.

•Muscle/nerve biopsy: It is required in selected cases of myopathy or neuropathy.

Step 4: Management

1.Airway protection—indications

•Bulbar palsy leading to dysarthria, dysphonia, dysphagia, and poor gag reflex

•Acute aspiration leading to respiratory arrest

Insidious aspiration leading to pneumonia and gradual respiratory decompensation

2.Respiratory support

Bedside tests and clinical assessment determine the need for respiratory support.

•ICU admission is needed if vital capacity is less than 1 L or less than 50% predicted value, respiratory rate more than 30, or if the patient is unable to maintain patent airway.

•Arterial blood gas analysis should be performed regularly. Hypoxia and hypercarbia with respiratory acidosis are late features. The patient may need

assisted ventilation even with normal blood gas in neuromuscular respiratory failure.

•Early tracheotomy should be considered in patients who require prolonged ventilatory support.

•Physiotherapy should be encouraged.

3.Nutritional support

•Enteral nutrition should be initiated as soon as the patient becomes hemodynamically stable.

•Nasogastric route should be preferred. Proper precaution should be taken to prevent regurgitation and aspiration. Head end should be elevated. Give prokinetics. Give continuous feed through enteral pump and check residual volume. Start nasojejunal feed in selected cases.

•Oral feed can be considered in some tracheotomized patients after proper swallowing assessment.

•Percutaneous endoscopic gastrostomy may be required for long-term use.

4.Venous thromboembolism prevention

•Due to immobilization, the risk of deep venous thrombosis and pulmonary embolism (PE) is high.

•Low-molecular-weight heparin or unfractionated heparin and gradient compression stockings are useful.

•Passive leg exercises should be initiated.

5.Pain control

•Both acute and chronic pain should be treated.

•Opioid analgesics, anticonvulsants, or antidepressants may be used for neuropathic pains.

6.Autonomic disturbance

•Common in small fibre neuropathies.

•Depending on the symptoms—treat excessive secretions with anticholinergics.

•b-Blocker for disproportionate tachycardia—cardiac pacing can be done for severe symptomatic bradycardia.

7.Pressure sores

•Frequent turning should be done and pressure-relieving mattresses should be used.

8.Physiotherapy

•It is important in the early course of the disease and in rehabilitation.

•Passive exercises, cough assist devices, and splints are useful.

9.Specific treatment

•Depending on the etiology

29.1Specific Illnesses

1.Critical illness neuropathy

•History will be suggestive of some critical illness, for example, sepsis, severe trauma, or burns.

•Clinical signs include generalized flaccid weakness with distal predominance and absent or decreased deep tendon reflexes. Facial and bulbar muscles are usually spared. Pain or paresthesia is not seen.

•Sensorium is intact.

•It often presents as failure to wean from the ventilator.

•Investigations: NCV studies will reveal decreased amplitude of motor and sensory action potentials with preserved conduction velocity, suggestive of an axonal neuropathy. EMG will reveal fibrillations and decreased motor unit potentials. CSF is almost always normal.

•It is diagnosed after excluding other neuropathies or neuromuscular junction abnormalities.

•Treatment is supportive care, intense glucose control, and early treatment of sepsis.

•Recovery is spontaneous in 3–6 months and is often partial.

•Prognosis depends on the underlying illness.

2.Critical illness myopathy

•It is difficult to distinguish clinically from its neuropathic counterpart, and both may occur concurrently.

•It usually occurs in patients with acute respiratory distress syndrome or severe asthma, who have been treated with intravenous corticosteroids, aminoglycosides and nondepolarizing neuromuscular blocking agents, or both.

•Plasma creatine kinase levels are transiently and marginally elevated.

•EMG shows small-amplitude, short-duration, polyphasic motor unit potentials, and sensory nerve conduction studies are normal.

•Repetitive nerve stimulation studies should be performed to exclude a defect of neuromuscular transmission caused by defective clearance of neuromuscular blocking agents.

•Treatment is supportive care, intense glucose control, and early treatment of sepsis.

•Recovery is spontaneous in 3–6 months and is often partial.

•Prognosis depends on the underlying illness.

3.GBS syndrome

•History of acute gastrointestinal or respiratory tract infection 1–3 weeks before the onset of neurological symptoms is present in 70% cases. Predisposing factors such as HIV infection, Hodgkin’s disease, history of recent immunization, recent surgery, and organ transplant should be sought.

•It begins with paresthesia in the legs followed by rapidly ascending weakness which can progress up to a month.

•Usually there is symmetric weakness in both proximal and distal muscle groups with loss or attenuation of deep tendon jerks. Objective sensory loss is mild. Bifacial and bulbar muscle involvement is frequently present. Autonomic dysfunction and respiratory involvement may occur in the acute stage and may be fatal.

•Investigations are usually normal in the first week of illness. CSF examination later reveals albuminocytologic dissociation with normal CSF glucose.

Note: In severe infection, the above-mentioned antibiotics may still be used if no other alternative exists

Electrodiagnostic studies may reveal only abnormalities of F waves in the beginning. This is followed by other features of demyelination such as prolonged distal latencies and decreased conduction velocities. MRI of spinal cord shows enhancement of lumbar nerve roots in some cases.

•Treatment

–Intravenous Immunoglobulin (IV IG) 400 mg/kg/day for 5 days

–Plasmapheresis 40–50 mL/kg/exchange(total 200–250 mL/kg) in three to five exchanges over 7–14 days

4.Myasthenia gravis (autoimmune disorder characterized by muscle weakness and exaggerated muscle fatigue)

•The patient requires admission to the ICU when there is impending/full-blown myasthenic crisis. This is characterized by dramatic worsening particularly of respiratory symptoms and bulbar weakness.

•Predisposing factors for crisis are systemic infections, drugs (Table 29.5), exacerbating weakness, surgery, and anesthesia.

•It commonly begins with fluctuating and asymmetric ptosis and weakness of extraocular muscles. This may be followed by weakness of bulbar and proximal limb muscles. Respiratory muscle involvement indicates myasthenic crisis. Muscle bulk, tone, reflexes, and sensory examination are normal.

•Investigations: Serum anti-acetylcholine receptor antibodies are positive in more than 90% cases of generalized myasthenia. Some seronegative patients have anti-muscle-specific tyrosine kinase antibodies. Edrophonium test: Pretreat with 0.5 mg atropine, give 2 mg edrophonium intravenously, and then give 3 mg and then 5 mg edrophonium intravenously; observe at each dose for 1–3 min for increase in muscle strength. Electrodiagnostic tests reveal decremental (15% or more reduction in amplitude) response in compound muscle action potential on repetitive nerve stimulation (RNS). Chest imaging should be done to rule out thymoma.

•Treatment

–Plasmapheresis 50 mL/kg/exchange)(total 200–250 mL/kg) in five to six exchanges over 7–14 days.

–IV IG 400 mg/kg/day for 5 days (preferred if severe infection coexists).

–Corticosteroids 1.5–2 mg/kg/day. In about one-third of patients, myasthenic weakness worsens 7–10 days after starting steroids.

–Steroid sparing—azathioprine, cyclosporine, mycophenolate mofetil.