Hemiplegia is not a progressive disorder, except in progressive conditions like a growing brain tumour. Once the injury has occurred, the symptoms should not worsen. However, because of lack of mobility, other complications can occur. Complications may include muscle and joint stiffness, loss of aerobic fitness, muscle spasms, bed sores, pressure ulcers and blood clots.

Sudden recovery from hemiplegia is very rare. Many of the individuals will have limited recovery, but the majority will improve from intensive, specialised rehabilitation. Potential to progress may differ in cerebral palsy, compared to adult acquired brain injury. It is vital to integrate the hemiplegic child into society and encourage them in their daily living activities. With time, some individuals may make remarkable progress.

The most common cause of hemiparesis and hemiplegia is stroke. Strokes can cause a variety of movement disorders, depending on the location and severity of the lesion. Hemiplegia is common when the stroke affects the corticospinal tract. Other causes of hemiplegia include spinal cord injury, specifically Brown-Séquard syndrome, traumatic brain injury, or disease affecting the brain. As a lesion that results in hemiplegia occurs in the brain or spinal cord, hemiplegic muscles display features of the upper motor neuron syndrome. Features other than weakness include decreased movement control, clonus (a series of involuntary rapid muscle contractions), spasticity, exaggerated deep tendon reflexes and decreased endurance.

The incidence of hemiplegia is much higher in premature babies than term babies. There is also a high incidence of hemiplegia during pregnancy and experts believe that this may be related to either a traumatic delivery, use of forceps or some event which causes brain injury.

Other causes of hemiplegia in adults include trauma, bleeding, brain infections and cancers. Individuals who have uncontrolled diabetes, hypertension or those who smoke have a higher chance of developing a stroke. Weakness on one side of the face may occur and may be due to a viral infection, stroke or a cancer.

Klumpke's paralysis is a form of paralysis involving the muscles of the forearm and hand, resulting from a brachial plexus injury in which the eighth cervical (C8) and first thoracic (T1) nerves are injured either before or after they have joined to form the lower trunk. The subsequent paralysis affects, principally, the intrinsic muscles of the hand (notably the interossei, thenar and hypothenar muscles) and the flexors of the wrist and fingers (notably flexor carpi ulnaris and ulnar half of the flexor digitorum profundus). Forearm pronators and wrist flexors may be involved, as may dilators of the iris and elevators of the eyelid (both of which may be seen in the case of associated Horner's syndrome). The classic presentation of Klumpke's palsy is the “claw hand” where the forearm is supinated and the wrist and fingers are flexed. If Horner syndrome is present, there is miosis (constriction of the pupils) in the affected eye.

The injury can result from difficulties in childbirth. The most common aetiological mechanism is caused by a traumatic vaginal delivery. The risk is greater when the mother is small or when the infant is of large weight. Risk of injury to the lower brachial plexus results from traction on an abducted arm, as with an infant being pulled from the birth canal by an extended arm above the head or with someone catching himself by a branch as he falls from a tree. Lower brachial plexus injuries should be distinguished from upper brachial plexus injuries, which can also result from birth trauma but give a different syndrome of weakness known as Erb's palsy.

Other trauma, such as motorcycle accidents, that have similar spinal cord injuries to C-8 & T-1, also show the same symptom's of Klumpke's paralysis.

Klumpke's paralysis (or Klumpke's palsy or Dejerine–Klumpke palsy) is a variety of partial of the lower roots of the brachial plexus. The brachial plexus is a network of spinal nerves that originates in the back of the neck, extends through the axilla (armpit), and gives rise to nerves to the upper limb. (see picture - click to enlarge). It is named after Augusta Déjerine-Klumpke.

Triplegia is a medical condition characterized by the paralysis of three limbs (Triplegia Muscle Anatomy) . A person with triplegia can be referred to as triplegic. While there is no typical pattern of involvement, it is usually associated with paralysis of both legs and one arm — but can also involve both arms and one leg. Triplegia can sometimes by considered a combination of hemiplegia (paralysis of arm and leg of one side of the body) overlaying diplegia (paralysis of both legs), or as quadriplegia (paralysis of four limbs) with less involvement in one extremity.

The condition is commonly associated with cerebral palsy, although conditions such as stroke can also lead to it. Triplegia has also been found to be due to an increase in intracranial pressure associated with hydrocephalus resulting from traumatic brain injury.

A similar condition is triparesis, in which the patient suffers from paresis in three limbs, meaning that the limbs are very weak, but not completely paralyzed.

In a case reported only due to its rarity, triplegia was reported following a tonsillectomy (surgical removal of the tonsils). An eight-year-old male patient was sent to Willard Parker Hospital on August 12, 1929 and had been diagnosed with poliomyelitis. After an unrelated, and routine, tonsillectomy there was complete flaccid paralysis and loss of feeling in both the legs, right arm, and muscles in the trunk.

Most common causes of lower motor neuron injuries are trauma to peripheral nerves that serve the axons – a virus that selectively attacks ventral horn cells.

Disuse atrophy of the muscle occurs i.e., shrinkage of muscle fibre finally replaced by fibrous tissue (fibrous muscle)

Other causes include Guillain–Barré syndrome, "C. botulism", polio, and cauda equina syndrome; another common cause of lower motor neuron degeneration is amyotrophic lateral sclerosis.

Paresis () is a condition typified by a weakness of voluntary movement, or partial loss of voluntary movement or by impaired movement. When used without qualifiers, it usually refers to the limbs, but it can also be used to describe the muscles of the eyes (ophthalmoparesis), the stomach (gastroparesis), and also the vocal cords (Vocal cord paresis). Neurologists use the term "paresis" to describe weakness, and "plegia" to describe paralysis in which all voluntary movement is lost. The term "paresis" comes from the "letting go" from παρίημι "to let go, to let fall".

Jugular foramen syndrome, or Vernet's syndrome is characterized by the paresis of 9th–11th (with or without 12th) cranial nerves together.

Almost all cases of synkinesis develop as a sequel to nerve trauma (the exception is when it is congenitally acquired as in Duane-Retraction Syndrome and Marcus Gunn phenomenon). Trauma to the nerve can be induced in cases such as surgical procedures, nerve inflammation, neuroma

, and physical injury.

Synkinesis is the result from miswiring of nerves after trauma. This result is manifested through involuntary muscular movements accompanying voluntary movements. For example, voluntary smiling will induce an involuntary contraction of the eye muscles causing the eye to squint when smiling. Most commonly involved are facial muscles and the extraocular muscles, rarely the hands are performing mirror movements.

Causes are diverse and include nerve trauma with improper healing, or nerve degeneration, as in the course of Parkinson´s disease. In congenital cases, mutations of genes involved in nerve growth, specifically axonal growth have been found. Rarely, it is part of syndromes with neuroendocrine problems such as Kallman syndrome.

The prognosis is usually good with normal intelligence and lifespan. Treatment depends on the cause, but is largely conservative with facial retraining or mime therapy, if needed, while Botox and surgery are used as last resort.

The cause of Todd's paresis been attributed to the affected cortex being ‘exhausted’ or silenced due to increased inhibition, but these conjectures are not supported. It has been observed that the impairments that follow seizures are similar to those that follow strokes, where for a period of time blood flow to certain areas of the brain is restricted and these areas are starved of oxygen.

The most significant issue regarding the Todd's paresis is its differentiation from a stroke. The issue is further complicated by the fact that some strokes trigger a focal seizure during the acute phase. A Todd's paresis in this context may overestimate the extent of neurological deficit due to the vascular process itself resulting in erroneous decisions with regards to acute stroke therapy such as thrombolysis. For this reason a seizure during an acute stroke is generally accepted to be a relative contraindication to thrombolytic therapy, especially in the absence of documented cerebrovascular occlusion using vascular imaging techniques.

An infant with Todd's paresis does not necessarily preclude the diagnosis of a febrile convulsion. This view is as a result of a recent study that showed the incidence of Todd's paresis to be in 0.4% of infants that have been diagnosed with a febrile convulsion.

Parinaud's syndrome, also known as dorsal midbrain syndrome, vertical gaze palsy, and Sunset Sign, is an inability to move the eyes up and down. It is caused by compression of the vertical gaze center at the rostral interstitial nucleus of medial longitudinal fasciculus (riMLF). The eyes lose the ability to move upward and down .

It is a group of abnormalities of eye movement and pupil dysfunction. It is caused by lesions of the upper brain stem and is named for Henri Parinaud (1844–1905), considered to be the father of French ophthalmology.

A lower motor neuron lesion is a lesion which affects nerve fibers traveling from the ventral horn or anterior grey column of the spinal cord to the relevant muscle(s) – the lower motor neuron.

One major characteristic used to identify a lower motor neuron lesion is flaccid paralysis – paralysis accompanied by loss of muscle tone. This is in contrast to an upper motor neuron lesion, which often presents with spastic paralysis – paralysis accompanied by severe hypertonia.

Ophthalmoparesis or ophthalmoplegia refers to weakness (-paresis) or paralysis (-plegia) of one or more extraocular muscles which are responsible for eye movements. It is a physical finding in certain neurologic, ophthalmologic, and endocrine disease.

Internal ophthalmoplegia means involvement limited to the pupillary sphincter and ciliary muscle. External ophthalmoplegia refers to involvement of only the extraocular muscles. Complete ophthalmoplegia indicates involvement of both.

Parinaud's Syndrome results from injury, either direct or compressive, to the dorsal midbrain. Specifically, compression or ischemic damage of the mesencephalic tectum, including the superior colliculus adjacent oculomotor (origin of cranial nerve III) and Edinger-Westphal nuclei, causing dysfunction to the motor function of the eye.

Classically, it has been associated with three major groups:

1. Young patients with brain tumors in the pineal gland or midbrain: pinealoma (intracranial germinomas) are the most common lesion producing this syndrome.

2. Women in their 20s-30s with multiple sclerosis

3. Older patients following stroke of the upper brainstem

However, any other compression, ischemia or damage to this region can produce these phenomena: obstructive hydrocephalus, midbrain hemorrhage, cerebral arteriovenous malformation, trauma and brainstem toxoplasmosis infection. Neoplasms and giant aneurysms of the posterior fossa have also been associated with the midbrain syndrome.

Vertical supranuclear ophthalmoplegia has also been associated with metabolic disorders, such as Niemann-Pick disease, Wilson's disease, kernicterus, and barbiturate overdose.

A gaze palsy is the paresis of conjugate eye movements.

Horizontal gaze palsy may be caused by lesions in the cerebral hemispheres, which cause paresis of gaze away from the side of the lesion, or from brain stem lesions, which, if they occur below the crossing of the fibers from the frontal eye fields in the caudal midbrain, will cause weakness of gaze toward the side of the lesion. These will result in horizontal gaze deviations from unopposed action of the unaffected extraocular muscles. Another way to remember this is that patients with hemisphere lesions look towards their lesion, while patients with pontine gaze palsies look away from their lesions. Note that patients with gaze palsy still have conjugate eye movements and therefore do not complain of diplopia.

The human Robo gene acts as a receptor for a midline repulsive cue. When Robo is mutated, the longitudinal tract formation is disrupted and therefore normal neuronal connections cannot form. This leads to the reduced hindbrain volume and scoliosis, which are common symptoms of horizontal gaze palsy.

Adie's syndrome is not life-threatening or disabling. As such, there is no mortality rate relating to the condition; however, loss of deep tendon reflexes is permanent and may progress over time.

Ophthalmoparesis can result from disorders of various parts of the eye and nervous system:

- Infection around the eye. Ophthalmoplegia is an important finding in orbital cellulitis.

- The orbit of the eye, including mechanical restrictions of eye movement, as in Graves disease.

- The muscle, as in progressive external ophthalmoplegia or Kearns-Sayre syndrome.

- The neuromuscular junction, as in myasthenia gravis.

- The relevant cranial nerves (specifically the oculomotor, trochlear, and abducens), as in cavernous sinus syndrome or raised intracranial pressure.

- The brainstem nuclei of these nerves, as in certain patterns of brainstem stroke such as Foville's syndrome.

- White matter tracts connecting these nuclei, as in internuclear ophthalmoplegia, an occasional finding in multiple sclerosis.

- Dorsal midbrain structures, as in Parinaud's syndrome.

- Certain parts of the cerebral cortex (including the frontal eye fields), as in stroke.

- Toxic envenomation by mambas, taipans, and kraits.

Thiamine deficiency can cause ophthalmoparesis in susceptible persons; this is part of the syndrome called Wernicke encephalopathy. The causal pathway by which this occurs is unknown. Intoxication with certain substances, such as phenytoin, can also cause ophthalmoparesis.

Strokes are one of the most common causes of Foix-Chavany-Marie Syndrome. The type of strokes associated with this syndrome include embolic and thrombotic strokes. Strokes affecting the middle cerebral artery and the branches that pass through or near the operculum are characteristic of FCMS.

Symptoms of infections specifically HIV and Herpes simplex encephalitis can cause FCMS. Numerous lesions can develop with HIV infections, which likely result in the development of FCMS.

Adie syndrome is a neurological disorder characterized by a tonically dilated pupil that reacts slowly to light but shows a more definite response to accommodation (i.e., light-near dissociation). It is frequently seen in females with absent knee or ankle jerks and impaired sweating. It is named after the British neurologist William John Adie. It is caused by damage to the postganglionic fibers of the parasympathetic innervation of the eye, usually by a viral or bacterial infection which causes inflammation, and affects the pupil of the eye and the autonomic nervous system.

Symptoms of this syndrome are consequences of this paresis. As such, in an affected patient, you may find:

- dysphonia/hoarseness

- soft palate dropping

- deviation of the uvula towards the normal side

- dysphagia

- loss of sensory function from the posterior 1/3 of the tongue

- decrease in the parotid gland secretion

- loss of gag reflex

- sternocleidomastoid and trapezius muscles paresis

In medicine, split hand syndrome is a neurological syndrome in which the hand muscles on the side of the thumb (lateral, thenar eminence) appear wasted, whereas the muscles on the side of the little finger (medial, hypothenar eminence) are spared. Anatomically, the abductor pollicis brevis and first dorsal interosseous muscle are more wasted than the abductor digiti minimi.

If lesions affecting the branches of the ulnar nerve that run to the wasted muscles are excluded, the lesion is almost sure to be located in the anterior horn of the spinal cord at the C8-T1 level. It has been proposed as a relatively specific sign for amyotrophic lateral sclerosis (ALS or Lou Gehrig's disease). It can also occur in other disorders affecting the anterior horn, such as spinal muscular atrophy, Charcot-Marie-Tooth disease, poliomyelitis and progressive muscular atrophy. A slow onset and a lack of pain or sensorial symptoms are arguments against a lesion of the spinal root or plexus brachialis. To an extent, these features can also be seen in normal aging (although technically, the apparent muscle wasting is sarcopenia rather than atrophy).

The term split hand syndrome was first coined in 1994 by a researcher from the Cleveland Clinic called Asa J. Wilbourn.

A somatosensory disorder is an impairment of the somatosensory system.