ABNORMAL MOVEMENTS AND DIFFICULTY WALKING DUE TO CENTRAL NERVOUS SYSTEM PROBLEMS

chapter 13


Abnormal Movements and Difficulty Walking Due to Central Nervous System Problems


In the previous chapter difficulty walking that is related to peripheral nervous system problems was discussed. The first half of this chapter deals with the more common central nervous system problems that result in difficulty walking; the second half discusses abnormal movements affecting the face, head and limbs, some of which lead to difficulty walking.


Difficulty walking related to weakness and/or sensory disturbances in one or both lower limbs occurs with spinal cord, brainstem or cerebral hemisphere problems affecting the motor and/or sensory pathways. Unsteadiness in the legs in the absence of weakness can occur with vertigo or with problems in the cerebellar pathways including the cerebellar connections in the brainstem, in the extrapyramidal system such as Parkinson’s syndrome or a frontal lobe disorder referred to as an apraxic gait. Patients with severe visual impairment due to either ocular or occipital lobe problems will have difficulty walking but this is not discussed in this chapter.



image ‘My legs are weak, Doc.’ When a patient states that their legs are weak, ask them to clarify exactly what they mean. Patients often use the term weakness as a non-specific way to say that something is wrong with their legs, and they do not necessarily mean that there is an actual loss of strength in their legs. Often, in fact, the legs are strong and the difficulty relates to other neurological and non-neurological problems.



DIFFICULTY WALKING


When a patient complains that they are have difficulty walking, simply ask if the difficulty relates to a sense of instability in the head or something wrong with their legs or if they are uncertain why they are having problems. Figure 13.1 shows the diagnostic possibilities in each of these three scenarios.




Difficulty walking related to weakness


The presence of weakness in the legs infers a problem involving the motor pathway, which extends from the motor cortex to the muscle.


One needs to determine if the weakness is related to spinal cord, brain stem or cerebral hemisphere pathology. This can be very difficult if weakness is the only symptom. Although bilateral leg weakness is more common in patients with spinal cord problems, it can occur in conditions that affect the brainstem and very rarely the parafalcine region of the cerebral hemispheres. Unilateral leg weakness is more in keeping with a cerebral hemisphere problem but, once again, can occur with brainstem or spinal cord involvement. Some potential clues that may help determine the site of the pathology are listed below.


Clues that the spinal cord is the site of the problem:



Clues that the brainstem is the site of the problem:



Clues that the cerebral hemisphere is the site of the problem:



• When there is upper motor neuron facial weakness in addition to the weakness in the arm and leg, the lesion must be above the mid pons on the contralateral side and, therefore, cannot be any lower in the brainstem or in the spinal cord. If areas in the hemispheres other than the motor pathway are affected, it may be possible to localise the lesion to the hemispheres, in particular the cerebral cortex.


• Dysphasia (dominant hemisphere lesions affecting the cortex)


• Gerstmann’s syndrome


• Visual field loss (hemianopia or quadrantanopia) if the visual pathways are affected


• Visual inattention if the parietal cortex is affected


• Cortical sensory signs (2-point discrimination, graphaesthesia, stereognosis or sensory inattention) (Other cortical phenomena are described in Chapter 5, ‘The cerebral hemispheres and cerebellum’.)



SPINAL CORD PROBLEMS


The three common spinal cord problems that result in leg weakness are cervical spondylitic myelopathy, thoracic cord compression, most often due to malignancy, and transverse myelitis.


There are many other rarer conditions that can affect the spinal cord and are traditionally divided into:



These are very rare conditions and are beyond the scope of this book.


The features that point to intrinsic cord pathology are:



No neurology textbook would be complete without mentioning the Brown–Sequard hemicord syndrome that consists of ipsilateral weakness and ipsilateral impairment of vibration and proprioception with contralateral impairment of pain and temperature sensation indicative of involvement of one half of the spinal cord. The explanation for this clinical syndrome is that the motor fibres and dorsal columns cross the midline at the level of the foramen magnum while the spinothalamic tract crosses in the spinal cord close to the entry into the spinal cord of the dorsal nerve root conveying sensation.



Cervical spondylotic myelopathy (CSM): Cervical spondylotic myelopathy (CSM) is the commonest cause of spinal cord dysfunction in elderly patients. It is also the commonest cause of paraparesis or quadriparesis not related to trauma. Repeated occupational trauma, such as carrying axial loads, genetic predisposition and Down syndrome all predispose to an increased risk of cervical spondylosis.


Cervical spondylosis relates to degenerative changes initially in the cervical discs with subsequent subperiosteal bone formation, referred to as osteophytes. Cervical disc protrusion or extrusion, osteophytes and hypertrophy of the ligamentum flavum together result in spinal cord compression, and secondary spinal cord ischaemia can occur with severe compression. Rarely spondylolisthesis may occur and cause cord compression.


Cervical cord compression (see Figure 13.2) can be seen in younger patients with congenitally narrow spinal canals (10–13 mm). The spinal cord is stretched during flexion of the cervical spine and buckling of the ligamentum flavum occurs during extension of the cervical spine. Thus, repeated flexion and extension in the patient with significant canal narrowing may cause intermittent acute compression of the spinal cord, and it is thought that this may also account for the clinical deterioration seen in many cases of CSM [1].



The natural course of CSM for any given individual is variable and precise prognostication is not possible. Once moderate signs and symptoms develop, however, patients are less likely to spontaneously improve. Worsening occurs more commonly in older patients whereas patients with mild disability are less likely to worsen [1].


CSM can present in a variety of ways.



1. The commonest presentation is with the insidious onset of difficulty walking related to weakness and/or stiffness (due to spasticity). Some patients will have neck pain from the cervical spondylosis; pain in the arm related to nerve root compression is less common.


2. Older patients in particular may present with weakness and wasting of the small muscles of the hands related to nerve root compression, and the signs of spinal cord compression are noted when they are examined.


3. A presentation that is much less common is the central cord syndrome resulting from a hyperextension injury in the setting of cervical canal stenosis where the weakness is greater in the upper than the lower limbs with or without a suspended sensory loss (affecting the shoulders and upper torso like a cape) and urinary retention.


4. Patients with cervical cord compression may experience an electric shock-like ensation radiating down their back or into their limbs with neck flexion, the so-called L’Hermitte phenomena commonly seen in patients with multiple sclerosis (MS).


The examination will reveal someone who may walk with a stiff-legged gait if there is associated spasticity, the tone will be increased with or without sustained ankle clonus, the knee reflexes will be abnormally brisk; ankle reflexes are often absent in the elderly and this should not exclude consideration of cervical cord compression. The plantar should be up-going but this is not universal.



image Some elderly patients assume that the gradual onset of difficulty walking is simply the result of advancing age and tend not to seek medical attention until the cord compression and limb weakness are severe.



MANAGEMENT of CERVICAL SPONDYLOTIC MYELOPATHY




Treatment


There are no prospective randomised controlled trials comparing medical management with surgery for CSM. The choice of therapy will be dictated by the patient’s attitude to surgery, the severity of the cervical cord compression and the fitness from the medical point of view of the patient to undergo surgery. Patients are advised that the goal of surgery is to prevent worsening and that improvement cannot be guaranteed, although many patients do in fact improve following appropriate surgery. Many neurosurgeons would recommend a period of observation in patients with mild symptoms and signs, but it would seem reasonable to recommend surgery for patients with moderate disability. Once moderate signs and symptoms develop, however, patients are less likely to spontaneously improve and such patients should consider surgical decompression.



Thoracic cord compression: Thoracic spinal cord compression most commonly occurs with metastatic malignancy, less commonly with a thoracic disc, epidural abscess or extrinsic spinal cord tumour such as a meningioma or a neurofibroma. There is an aphorism that ‘a thoracic cord lesion in a middle-aged to elderly female is a meningioma (benign tumour arising from the meninges) until proven otherwise’. Back pain is rare with a meningioma, more common but not a universal feature of thoracic discs, but increasingly severe back pain occurs for on average 8 weeks or longer in 80–95% of patients who subsequently develop malignant cord compression [2]. Patients who are not known to suffer from malignancy, but who develop increasingly severe midline (especially thoracic) back pain, should be investigated promptly in the hope of preventing malignant cord compression.


Although initially the pain is localised to the vertebra, subsequent nerve root compression can result in radicular pain. The back pain is often worse after lying down and this can be a vital clue. Rapidly developing weakness in the legs is the initial and dominant neurological symptom once malignant spinal cord compression occurs; sensory symptoms are less common and sphincter disturbance occurs late. A delay in the diagnosis of malignant cord compression is common with many patients only diagnosed after they lose their ability to walk [2, 3] and, unfortunately, once significant cord compression related to malignancy occurs the prognosis for recovery is poor.


In patients with preexisting malignancy, particularly breast and prostate, the development of back pain should raise the suspicion of possible secondary malignancy in the spinal column and prompt investigation (see Figure 13.3).



The following suggest spinal metastases:



It has been recommended that patients with known malignancy should be advised to return urgently within 24 hours for review should they develop back pain in the midline [4].


Severe thoracic back pain followed by the rapid development of spinal cord compression can be the initial manifestation of malignancy in as many as one-third of patients with cancer of unknown primary origin, non-Hodgkin lymphoma, myeloma and lung cancer [2]. Metastatic disease less commonly affects the cervical or lumbar spine. Although almost any systemic cancer can metastasise to the spinal column, prostate, breast and lung are the most common [2].



MANAGEMENT of MALIGNANT CORD COMPRESSION






Intrinsic spinal cord problems: Transverse myelitis is the commonest intrinsic cord lesion resulting in dysfunction in the lower limbs and difficulty walking in the younger patient while spinal cord ischaemia is seen in the elderly. Spinal cord ischaemia can develope abruptly or insidiously. Other intrinsic spinal cord problems such as tumours and the cavitating lesion referred to as syringomyelia are very rare and are beyond the scope of this book.



TRANSVERSE MYELITIS: Acute transverse myelitis (ATM) is a focal inflammatory disorder of the spinal cord, resulting in motor, sensory and autonomic dysfunction with many infectious and non-infectious causes [10].


The Transverse Myelitis Consortium Working Group [11] has established diagnostic criteria that require:



The development of neurological symptoms and signs is often preceded by a febrile illness up to 4 weeks prior to onset [12], typically an upper respiratory tract infection. Patients present with an ascending sensory loss, with the development of a sensory level in the majority of patients with or without a paraparesis, paraplegia, quadriplegia and urinary retention [12, 13]. The symptoms may develop rapidly over as little as 4 hours or more slowly over several weeks.



image Patients whose spinal cord symptoms reach maximal severity in < 4 hours from onset should be presumed to have an ischaemic aetiology [1].


In one study of acute transverse myelitis, a parainfectious cause was diagnosed in 38% of patients but the underlying infectious agent was identified in a minority of patients. In 36% of patients the aetiology remained uncertain and in 22% it was the first manifestation of possible MS. The MRI scan (see Figure 13.4) was abnormal in 96% of cases (i.e. a normal MRI is rare but does not exclude a diagnosis) [12].



Acute non-compressive myelopathies can also be classified according to their aetiology [14]:




MANAGEMENT of TRANSVERSE MYELITIS


Patients suspected of having transverse myelitis should have an MRI scan and a lumbar puncture.


The CSF is abnormal [14] with:



MRI scanning usually but not invariably reveals abnormalities that may be restricted to one or many spinal segments [13]. Typically the MRI signal changes extend at least three segments above the sensory level.


In western countries transverse myelitis may be the presenting feature of MS or it may manifest during the course of this disease. Patients who are ultimately diagnosed with MS are more likely to have asymmetric clinical findings, predominant sensory symptoms with relative sparing of motor systems, MRI lesions extending over fewer than two spinal segments, abnormal brain MRI and oligoclonal bands in the CSF [11]. It is important to test for oligoclonal bands in the CSF and serum to detect intrathecal synthesis seen with MS.



CONUS MEDULLARIS LESION: This chapter has discussed central nervous system causes of difficulty walking whereas the previous chapter discussed peripheral nervous system problems. There is one very rare syndrome that produces both upper and lower motor neuron signs in the lower limbs and this is a lesion at the level of the conus medullaris (the lower end of the spinal cord at the level of the 2nd lumbar vertebra) with or without the involvement of the cauda equina (the sheath of lumbosacral nerve that extends from the lower end of the spinal cord through the spinal canal exiting at the appropriate level and that looks like a horse’s tail, hence the name).


The clinical signs in a pure conus medullaris lesion consist of impaired sensation affecting the lower sacral nerve roots (S3–S5) with urinary retention and urinary or faecal incontinence. If the cauda equina is also involved there will be low back pain, weakness and sensory loss in the lower limbs that is asymmetrical, but it usually affects the lower lumbar and upper sacral nerve roots (L5–S1), resulting in foot drop and absent ankle reflexes.




CEREBRAL HEMISPHERE PROBLEMS CAUSING WEAKNESS IN THE LEG(S)


Weakness related to cerebral hemisphere problems is almost invariably unilateral, although bilateral lower limb weakness can occur with involvement of the parafalcine region, typically with cerebral infarction in the distribution of the anterior cerebral artery. The presence of abulia (see Chapter 5, ‘The cerebral hemispheres and cerebellum’) is the clue that the lesion is affecting the distribution of the anterior cerebral artery.


Cerebrovascular disease is the most likely cause of motor weakness related to the motor pathways in the cerebral hemispheres, either ischaemia or haemorrhage. Demyelinating diseases and both benign and malignant (primary or secondary) tumours are the other more common causes although both of these are rare. CT scanning, but in particular MRI scanning, can readily establish the pathology.



Difficulty walking due to unsteadiness


When patients complain that they are unsteady on their feet, it is important to clarify whether this sense of instability relates to a feeling of dizziness or instability in the head or whether it relates to something wrong in the legs suggesting a problem in either the spinal cord or peripheral nervous system.



UNSTEADINESS RELATED TO DIZZINESS IN THE HEAD


Vertigo is ‘an illusion of movement’, often rotary, with the sensation as if the room or head is spinning and it renders the patient unable to walk. The presence of vertigo with the head or room spinning clearly indicates the problem is either in the peripheral vestibular system, where there may be associated tinnitus and/or deafness, or in the brainstem where the presence of diplopia, weakness and sensory symptoms may accompany the vertigo.


A less marked vertigo includes a sensation of instability, a feeling of disequilibrium like being on a ship, but can also include sensations of tipping, tilting, falling etc. The more one strays from the sense of rotation, the less one can be sure that the problem causing instability is within the vestibular system. This sense of dizziness in the head could also relate to hypotension.



UNSTEADINESS IN THE ABSENCE OF WEAKNESS OR DIZZINESS


Patients with bilateral vestibular hypofunction (e.g. due to aminoglycoside toxicity) do not present with vertigo but with a sense of disequilibrium.


Patients with marked impairment of proprioception in the lower limbs will be very unsteady on their feet, particularly in the dark and when they close their eyes, e.g. while having a shower or washing their hair. This is often referred to as a sensory ataxia. Vitamin B12 deficiency with subacute combined degeneration of the cord is probably the commonest cause now that syphilis has largely been eradicated. Very rarely, impairment of proprioception results from a dorsal root ganglionopathy or sensory neuronopathy. This occurs as a paraneoplastic phenomenon [15, 16], in patients with Sjögren’s syndrome [17] or pyridoxine abuse [18]. The sensory ganglionopathies are extremely rare and are mentioned here because the neurological problem may antedate the diagnosis of malignancy or indicate recurrence in a patient with known malignancy and should prompt a search for malignancy [16].


Another cause of difficulty walking from unsteadiness in the absence of dizziness in the head or weakness in the legs is the ataxia related to cerebellar disease. Ataxia in the limbs reflects problems in the cerebellar hemispheres whereas ataxia affecting the trunk (truncal ataxia) is seen in patients with problems related to the midline vermis of the cerebellum.


Truncal ataxia occurs with hypothyroidism [19] and alcoholism [20]. Patients with isolated truncal ataxia walk with a wide-based gait with little in the way of nystagmus or ataxia in the limbs.


The commonest cause of ataxia related to cerebellar disease would be cerebellar infarction. Two less common causes of cerebellar ataxia affecting the cerebellar hemispheres are the paraneoplastic cerebellar syndrome [21] and the hereditary spinocerebellar atrophies (SCA) [22]. The paraneoplastic cerebellar syndrome may be the initial presenting symptom of malignancy or develop after the diagnosis of malignancy is established. The clinical picture is one of very disabling ataxia affecting the limbs and trunk, together with dysarthria and nystagmus evolving rapidly over days to weeks. On the other hand, the hereditary spinocerebellar atrophies present with the insidious onset of ataxia affecting the limbs with or without nystagmus and dysarthria.

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Jun 19, 2016 | Posted by in NEUROLOGY | Comments Off on ABNORMAL MOVEMENTS AND DIFFICULTY WALKING DUE TO CENTRAL NERVOUS SYSTEM PROBLEMS

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