Acute impairment of the normal walking pattern is a comparatively common sign in patients arriving in the emergency department. Many patients present their symptom of inability to walk with sufficient explanation, and quite often it is due to an inability to support one's own weight from leg weakness or to maintain balance. Differentiating muscle weakness, lack of balance, or even inability to initiate a walk requires careful assessment and most of the time emergent neuroimaging. Examination of strength, sensation, and coordination should elicit a localization, severity of illness, and further determination of the specific diagnosis. Statistically, the most serious acute disorders associated with leg weakness are those due to acute spinal cord compression, acute spinal cord ischemia, and Guillain-Barré syndrome. To preserve the notion that acute leg weakness may be due to spinal cord compression, a separate chapter (Chapter 12) details recognition and management. Disorders with acute ataxia in adults (viral illness predominates in children) are invariably due to acute cerebellar or pontine (vestibular nuclei) lesions (see Chapter 15). Acute ataxic hemi-paresis may be due to a pontine or capsular lesion (see Chapter 15).
If the patient walks into the emergency department, balance and gait can be examined by following a simple set of tests. Proprioception after standing is tested by assessing vertical posture with eyes closed. Ability to maintain vertical stance with eyes closed could be impaired, with patients veering to one side. (One should note that keeling over consistently toward the examiner is psychogenic.) Walking is assessed next. Failure to initiate walking, “freezing” of gait during walking through a door, stepping and stride, and arm swing (including turns) are noted. Tandem gait and side-to-side pushes are finally added to assess gait.
Failure to initiate gait and lifting the feet off the floor (“as if glued to the floor, magnetic”) may be due to acute frontal brain lesions or a more diffuse motor control failure, seen in patients with profound white matter lesions. Parkinsonian gait is usually suspected with small steps, audible shuffle, en bloc turns, and flexed posture. Freezing is common in parkinsonian syndromes and more a result of progression of the disease than an acute, first prominent manifestation.1,2Freezing may occur in a third of patients with hemiparetic stroke.3 Unilateral thalamus lesions with sensory loss but no motor weakness could result in falls from falling backward or sideways.4 The thalamofrontal connections and input from the cerebellum and spinal long tracts are responsible for this gait difficulty.
Gait apraxia is diagnosed when steps are inappropriate. Mayer and Barron5 defined it as “loss of ability to properly use the lower limbs in the act of walking.” Gait is counterproductive with perseverative leg movements, crossing legs while attempting to walk, and inability to mime march on the spot or wipe feet on an imagined mat.
Normally, during walking or running the feet slide very close to each other with minimal distance (less than 1 inch) between them. In cerebellar ataxia, the base widens and patients have instability of the trunk, poorly directed foot landing, and less specific inability to perform a tandem gait and sway and fall in all directions. Visual correction may reduce these manifestations. However, flocculonodular localizations do produce more sweep to one side with eyes closed.6Inability to even sit without falling over indicates a midline cerebellar vermis lesion.
Spastic gait with its typical scissoring and increased tone (rapid stretching causes increased resistance) proportionally involves the extensor muscles in the legs. Its presentation implies a much longer process, but patients may more or less acutely notice their symptoms becoming severe.
Loss of proprioception is a result of a disorder involving dorsal root ganglia cells and large fiber afferents in the posterior columns. These are usually known as “subacute” conditions due to prior use of chemotherapeutic agents such as cisplatin (dose >500 mg/m2), nitrous oxide (abuse by dentists), and overdose with pyridoxine, or due to paraneoplastic destruction (Box 2.1). Pseudo-athetosis, areflexia, and absent position and vibration sense are hallmarks of this entity. When seen with spastic paraparesis and Lhermitte's sign, a cervical myelopathy (e.g., cervical spondylosis or multiple sclerosis) should be considered. Patients may have useless, numb, clumsy hands and may be unable to identify simple objects (e.g., coins) in their hands.
Inability to support one's own weight due to leg weakness and inability to get up from a sitting position, climb stairs, or walk uphill without taking countermeasures may eventually evolve into full paraplegia. These symptoms are so prominent that they may obscure equally important complaints of tingling and numbness. Progression may be in the ascending direction or suddenly complete.
The first principle is to determine a pattern of weakness. Proximal involvement favors muscle disease, myasthenia gravis, or myasthenic syndromes but also spinal cord disease. Purely distal weakness is more typical of peripheral nerve disease. Periodic paralysis is a rare disorder, but this channelopathy should be considered if the symptoms are repetitive.10 Improving strength with repetitive testing argues for a presynaptic defect of the neuromuscular junction (Lambert-Eaton syndrome). Worsening strength with repetitive testing argues for a postsynaptic disorder of neuromuscular traffic (myasthenia gravis).11Tendon reflexes are lost early in acute polyradiculopathy and in spinal shock (see Chapter 12) and reduced in Lambert-Eaton syndrome and severe muscle disorders. Fasciculations and atrophy should be noted and indicate rapid worsening of a chronic neurologic disorder, mostly disorders involving the anterior horn cell or peripheral nerve. Muscle tone is flaccid in acute Guillain-Barré syndrome, spinal shock, or cauda equina lesion.
Box 2.1. Paraneoplastic Syndromes Affecting Gait
Disabling ataxia, leg weakness, pains, and paresthesias may be presenting manifestations of canter. Key syndromes are paraneoplastic cerebellar degeneration, opsoclonus, myoclonus and ataxia syndrome, sensory or motor polyneuropathy, and Lambert-Eaton syndrome. These manifestations are probably a result of a rapidly evolving immunologic mechanism and may become dramatically apparent in a matter of weeks. Paraneoplastic cerebellar degeneration associated with anti-Purkinje cell antibodies (PCA-1 or anti-Yo) increases suspicion of breast, ovarian, or genital tract cancer; when associated with ANNA (antineuronal nuclear autoantibody), anti-Ri, or anti-Hu, it predicts small cell lung cancer. In some patients. anti-Tr antibodies predict Hodgkin's lymphoma. Sensory neuropathies are associated with ANNA-1 or anti-Hu antibodies, which are rarely found in motor neuropathy. Voltage-gated calcium channel antibodies are almost always present in Lambert-Eaton syndrome. Positive antibodies should prompt more aggressive search using bronchoscopy, hone marrow aspiration, laparoscopy, or positron emission tomography. The serum antibodies that are Found vary in type and detection and do not predict response to therapy, if any.7,8,9
Neurologic examination proceeds with sensory examination of the dermatomes and bladder assessment. The methods are discussed in Chapter 12 regarding spinal cord compression, where it is most relevant.
The differential diagnosis of acute or worsening paraplegia is quite broad but here is tailored toward disorders that, when not met with immediate attention, may result in permanent disability, bladder dysfunction, or even imperil respiration (Table 2.1). Acute paraplegia may be an immediate consequence of aortic dissection. Acute pain may be associated with widening mediastinum on chest X-ray. An emergent echocardiogram or magnetic resonance angiogram can confirm the diagnosis. Ischemic myelopathy may be due to reduced spinal blood flow, which in turn is due to increased intraspinal cerebrospinal fluid (CSF) pressure (Box 2.2).
Many other neurologic disorders can mimic spinal cord compression. Essential facts in the medical history include recent viral illness, vaccinations, illicit drug use, fever, weight loss, myalgia, severe back pain with radiation, recent tick bite, and skin rash, which may indicate acute myelitis or polyradiculopathy. It is very important to determine whether the patient is immunocompromised (e.g., cyclosporine, non-Hodgkin's lymphoma), has clinical evidence of human immunodeficiency virus (HIV) infection, or has risk factors for the acquired immunodeficiency syndrome (AIDS) virus, including previous blood or blood-product transfusions (the risks were higher before 1985, when regular HIV screening was not available in blood banks). Recent travel may be relevant and may suggest a myelopathy from Schistosoma species (endemic in Brazil) or cysticercosis (any country in Latin America).
Table 2.1. Acute Paraplegia
Box 2.2. Paraplegia in Aortic Dissection
Immediate- or delayed-on set paraplegia from spinal cord ischemia can be a consequence of aortic dissection. It is often inappropriately considered permanent at onset. An acute lumbar puncture may lead to rapid recovery, and a high opening pressure is evident. Aortic occlusion of the descending aorta and cardiac outflow obstruction increase volume in the intracranial sinuses, translating into increased intraspinal volume and increased CSF pressure. Early spinal cord edema may cause the CSF pressure to rise also. Spinal cord perfusion is reduced and equal to spinal arterial pressure minus CSF pressure. Removal of 20 to 30 mL of CSF followed by continuous CSF drainage at a rate of 5 to 10 mL per hour can be dramatically effective, with resolution of symptoms within hours,12,13
Acute transverse myelitis should be considered in patients between age 10 and 20 or 30 and 40 years but is highly uncommon. Criteria include development of sensorimotor or autonomic dysfunction from a cord lesion, defined sensory level; bilateral signs that can be asymmetric; and progression to maximal deficit within hours or 3 weeks.
Line of Action
It is imperative to admit any patient with acute severe impairment of gait or balance and to expedite evaluation.
With so many possible levels of involvement in the nervous system, the laboratory tests should focus on the most probable localization (Fig. 2.1). Magnetic resonance imaging (MRI) is mandatory because compression of the thoracic or lumbar spinal cord or meningeal pathology is common in acute or rapidly worsening weakness (if no further localization can be made). It is not unreasonable to proceed with an MRI of the entire neuraxis to visualize all structures involved in gait initiation. If no structural lesions are found, cerebrospinal fluid examination is warranted.
CSF examination should follow and may be immediately therapeutic in patients with ischemic myelopathy associated with aortic dissection. Failure to recognize this option of removing CSF under high pressure may lead to permanent deficit.12
Infectious myelitis is the most common alternative diagnosis in acute spinal cord syndromes and often involves viral infections. Viruses affecting spinal gray matter usually include herpes zoster, but other herpes viruses (cytomegalovirus, herpes simplex) may attack nerve roots. CSF in herpes zoster myelitis shows pleocytosis, increased protein levels, and normal glucose values. Viruses with a proclivity for white matter include HIV and human T-cell lymphotropic virus (type I). A viral serologic panel should be obtained in the emergency department in appropriate cases (HSV-1, HSV-2, HHV-6, VZV, CMV, EBV, HIV, and enteroviruses). Increased white cell count should suggest an acute transverse myelitis. In appropriate circumstances such as in concurrent TB infection, CSF and fast bacilli smear and culture should be obtained. A moderate lymphocytic pleocytosis is common in acute transverse myelitis and may be accompanied by increased IgG and oligoclonal bands. Cytologic examination of CSF should focus on malignant cells (only 50% positive yield), and flow cytometry is indicated if atypical lymphocytes are found. Flow-cytometric immunophenotyping consists of antibodies against several antigens such as CD 19, CD45, and κ and λ immunoglobulin light chains to characterize a possible blast population or monoclonal B-cell population.
Figure 2.1 Critical steps in the evaluation of gait abnormalities or paraparesis. MR, magnetic resonance; CSF, cerebrospinal fluid; EMG/NCV, electromyography/nerve conduction velocity.
Oligoclonal bands in CSF suggest multiple sclerosis, particularly if other white matter lesions are found (up to 80% positive predictive value). Visual evoked potentials can be useful to document optic neuritis, as in Devic's disease or multiple sclerosis. Systemic inflammatory disease may be complicated by myelitis, and autoantibodies (ANA [antinuclear antibodies], double-stranded DNA, SS-A [RO], SS-B [La], Sm [Smith], and RNP [ribonucleoprotein]) are useful.
More peripherally, other important rapid discriminating tests in the emergency department are creatine kinase and nerve conduction studies with repetitive stimulation (presynaptic rapid stimulation results in incremental amplitude, postsynaptic decremental amplitude at low stimulation rate).14,15,16,17 Serum antibodies are tested for paraneoplastic syndromes, which can be quite rapid in presentation (Box 2.1).7,8,9 Muscle and nerve biopsy is needed to document inflammatory myopathy.
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