lacunar infarcts
Causes
Occlusion or blockage of one deep penetrating artery arising directly from the components of Circle of Willis basilar artery and cerebellar arteries causes Lacunar Infarct. This results in lesions in the brain’s deep nuclei (10% caudate, 14% thalamus and 37% putamen) and the internal capsule’s posterior limb (10%) or the pons (16%).
Carotid artery pathology from the heart, like in Atrial Fibrillation, can also lead to LACS.
Pathophysiology
The two proposed mechanisms responsible for LACS are known as microatheroma and lipohyalinosis. Initially, Lipohyalinosis was believed to be the principal small vessel pathology. Currently however, microatheroma is considered to be the mechanism which most frequently leads to arterial occlusion (stenosis). In some cases, when the parent artery develops an atheroma it blocks the opening of penetrating artery. This condition is called luminal atheroma. Sometimes, atheroma can also develop at the point of origin of the penetrating artery (junctional atheroma). The mechanism of hypoperfusion is occasionally believed to cause stenosis of penetrating artery as well. If the histologic examination does not show any evidence of the small vessel disease, the cause of the condition is believed to be associated with cardio-embolism or artery-to-artery embolism. A recent study shows that 25% of the total patients, in whom various radiological tests show defined lacunes, had developed the stroke due to potential cardiac causes.
Lacunar Infarcts commonly affect the basal ganglia and lenticular nucleus. Left Thalamic Lacunar Infarcts are very common in patients with this condition. In some rare cases, the infarctions occur in the deep cerebral white matter, the cerebellum and the anterior limb of the internal capsule. However, the cerebral surface, visual radiations and corpus callosum are not generally affected by the condition.
Signs and symptoms
The disorder is characterized by some common symptoms, including:
• Dizziness
• Loss of vision
• Loss of hearing
• Vertigo
• Balance problems
• Headache
The five different classical Lacunar Syndromes are characterized by different symptoms.
Symptoms of Pure Motor Stroke or Hemiparesis
This form is characterized by Hemiplegia or Hemiparesis that usually affects the arm, leg and face of one side. This results in difficulty in walking, speaking and using the hands. It may also cause Dysphagia and various transient sensory symptoms.
Symptoms of Ataxic Hemiparesis
It is marked by several motor and cerebellar symptoms such as clumsiness and weakness on the affected side of the patient’s body. The legs are more likely to get affected by this disorder compared to the arms. The onset of the symptoms often occurs over several hours or days.
Symptoms of Clumsy Hand or Dysarthria
Dysarthria, clumsiness and weakness of the affected hand are the most common symptoms of this form. These symptoms are often most prominent at the time of writing.
Symptoms of Pure Sensory Stroke
In this form of Lacunar Infarct, the patient experiences transient or persistent numbness, pain, tingling and burning sensations on one side of his or her body.
Symptoms of Mixed Sensorimotor Stroke
Its symptoms include Hemiplegia or Hemiparesis along with an ipsilateral sensory impairment.
Connect Biomechanics
Simple Walk-Cycle
Human walking is accomplished with a strategy called the double pendulum. During forward motion, the leg that leaves the ground swings forward from the hip. This sweep is the first pendulum. Then the leg strikes the ground with the heel and rolls through to the toe in a motion described as an inverted pendulum. The motion of the two legs is coordinated so that one foot or the other is always in contact with the ground. The process of walking recovers approximately sixty per cent of the energy used due to pendulum dynamics and ground reaction force.
Walking differs from a running gait in a number of ways. The most obvious is that during walking one leg always stays on the ground while the other is swinging. In running there is typically a ballistic phase where the runner is airborne with both feet in the air (for bipedals).
Another difference concerns the movement of the center of mass of the body. In walking the body "vaults" over the leg on the ground, raising the center of mass to its highest point as the leg passes the vertical, and dropping it to the lowest as the legs are spread apart. Essentially kinetic energy of forward motion is constantly being traded for a rise in potential energy. This is reversed in running where the center of mass is at its lowest as the leg is vertical. This is because the impact of landing from the ballistic phase is absorbed by bending the leg and consequently storing energy in muscles and tendons. In running there is a conversion between kinetic, potential, and elastic energy.
There is an absolute limit on an individual's speed of walking (without special techniques such as those employed in speed walking) due to the upwards acceleration of the center of mass during a stride - if it's greater than the acceleration due to gravity the person will become airborne as they vault over the leg on the ground. Typically however, animals switch to a run at a lower speed than this due to energy efficiencies.
Exercise
Physiotherapy interventions are used in the rehabilitation of lacunar stroke. A physiotherapy program will improve joint range of motion of the paretic limb using passive range of motion exercises. When increases in activity are tolerated, and stability improvements are made, patients will progress from rolling to side-lying, to standing (with progressions to prone, quadruped, bridging, long-sitting and kneeling for example) and learn to transfer safely (from their bed to a chair or from a wheel chair to a car for example). Assistance and ambulation aids are used as required as the patient begins walking and lessened as function increases. Furthermore, splints and braces can be used to support limbs and joints to prevent complications such as contractures and spasticity. The rehabilitation healthcare team should also educate the patient and their family on common stroke symptoms.