Clinical and neurophysiologic features of the pure motor deficit syndrome caused by selective upper motor neuron lesion: contribution to a new neurological entity

14.1 Introduction

Almost 60 years ago, the first description of pure motor hemiplegia of supraspinal origin was published by Fisher and Curry . Their definition was as follows: “For present purposes a pure motor hemiplegia is defined as a paralysis complete or incomplete of the face, arm and leg on one side unaccompanied by sensory signs, visual field defect, dysphasia or apractagnosia.” “In the case of brainstem lesions the hemiplegia will be free of vertigo, deafness, tinnitus, diplopia, cerebellar ataxia and gross nystagmus.”

This definition covers only pure motor deficit (PMD) caused by brainstem and supratentorial lesions and does not include PMD due to the spinal cord lesion. In this chapter, we will describe PMD due to brain, brainstem and spinal cord lesions.

I would like to encompass specific lesion sites of the corticospinal tract (CST) involving brain, brainstem, and spinal cord through clinical and neurophysiologic documentation. Furthermore, I will show neurophysiological markers of PMD and their predictive values.

The special attention will be done to present and document PMD during surgery of intracranial blood vessels (aneurysms or vascular malformation) as well as brain, brainstem, and spinal cord tumors surgery.

Besides surgery, PMD may happen during endovascular treatment of cerebral and spinal cord vascular malformations during angioembolization and in patients with an intraoperative stroke. Transient changes in neurophysiological signals indicating PMD could be seen during vasospasm episodes.

14.2 Underlying pathology of pure motor deficit

I attempted to understand, based on a literature review and my own experience, the pathologic processes underlying PMD and the major associated factors contributing to its development, spontaneous, or iatrogenic in origin.

I propose a systematization of pathologies, which might eventually enable a more constructive clinical approach in evaluating and treating these patients:

1.
vascular origin: due to arterial thrombosis (established or transient ischemic attacks) or ischemic episodes plus mechanical factors secondary to hemorrhage or angioembolization;
2.
tumors: malignant or benign lesions;
3.
traumatic brain, brainstem, and spinal cord injury;
4.
demyelination: multiple sclerosis and other demyelinating diseases;
5.
surgically induced: during procedures involving directly or indirectly the brain, brainstem, and spinal cord;
6.
neurodegenerative diseases: amyotrophic lateral sclerosis, spinal muscular atrophy, hereditary spastic paraplegia ;
7.
supranuclear (pseudobulbar) palsy;
8.
infection of the central nervous system: neurocysticercosis, poliomyelitis, meningovascular neurosyphilis, tuberculosis of the central nervous system (CNS) ;
9.
deposit diseases: adrenoleukodystrophy; and
10.
osmotic demyelination syndrome (formerly designated central pontine myelinolysis): iatrogenic in most of the cases, it is secondary to excessively rapid correction of hyponatremia.

14.3 Diagnosis

Diagnosis of PMD is based on (1) clinical and neurological examination, (2) neuroimaging studies, (3) testing for neurophysiological markers, and (4) postmortem pathology.

14.3.1 Clinical and neurological examination

According to the symptoms, the physician will perform a pre- and postoperative neurological examination that could suggest this specific neurological syndrome.

PMD shows presence of central motor neuron deficit without accompanying sensory deficit affecting nociception (pain), equilibrioception (balance), proprioception and kinesthesia (joint motion and acceleration), sense of time, thermoception (temperature differences), or causing visual field defect (homonymous or heteronimus hemianopsia, quadrantanopsia, etc.), dysphasia, or apractagnosia.

In the case of brainstem lesions the hemiplegia will be free of vertigo, deafness, tinnitus, diplopia, cerebellar ataxia, and gross nystagmus.

Motor deficit could have different presentations: monoplegia or monoparesis of one upper or lower limb, paraplegia or paraparesis, tetraplegia or tetraparesis, motor deficit involving three limbs, motor cranial nerve palsy: facial palsy or paralysis, dysarthria (attributable to corticobulbar dysfunction), deviation of the tongue on protrusion of central origin, conjugate lateral gaze impairment, combinations of these symptoms and incomplete variant of locked-in syndrome.
Patient would be free of numbness and sensory ataxia, pain, feelings of tightness, tingling or burning, pins and needles, pruritus (itchiness), tingling, buzzing or vibrating sensations, visual field defects (homonymous or heteronimus hemianopsia, quadrantanopsia, etc.), dysphasia, deafness, or cerebellar ataxia.

It is necessary to perform a detailed neurological assessment to provide reliable measures using appropriate scales to evaluate the intensity of deficits and their evolution.

On examination we can find different degrees of motor weakness that can be tested by using the modified Medical Research Council scale (ranging from 0—no contraction to 5—normal motor strength) and House–Brackmann facial palsy scale (ranging from I—normal to VI—total paralysis, no movement), increased muscle tone (muscle stiffness) and muscle spasms, increased/exaggerated deep tendon reflexes in the paralyzed side 1–2 days after the injury (both decreased—flaccid paralysis—in acute period), positive Babinski sign, long-term patients can develop muscle and joint deformities especially growing children, a negative Romberg’s test, no dysmetria or dysdiadochokinesia, intact sensation to pinprick, vibration, touch, joint position sense, two-point discrimination, graphesthesia, stereognosis and tactile localization, temperature, and pain.

Visual field can be tested by confrontation visual field exam and by campimetry/perimetry.

14.3.2 Use of neuroimaging techniques

The development and important advances in the use of noninvasive, painless neuroimaging techniques, such as computed tomography scan, magnetic resonance imaging (MRI), functional MRI, and diffusion tensor imaging (DTI) tractography, allow one to study functional structure and brain, brainstem, and spinal cord-behavior relationships.

Patient-specific anatomy of CST and corticobulbar tract (CBT) can be obtained by using fusion image of the data obtained by navigated transcranial magnetic stimulation (TMS) and DTI tractography as it has been described in Fig. 14.1 . This methodology can correlate clinical picture with possible lesion of CST or CBT and make very precise topographic and anatomical diagnosis.

Figure 14.1, nTMS-based DTI tractography of the CST.

You're Reading a Preview

Become a Clinical Tree membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here