The most recognizable symptoms in Parkinson's disease are movement ("motor") related. Non-motor symptoms, which include autonomic dysfunction, neuropsychiatric problems (mood, cognition, behavior or thought alterations), and sensory (especially altered sense of smell) and sleep difficulties, are also common. Some of these non-motor symptoms may be present at the time of diagnosis.

Four motor symptoms are considered cardinal in PD: tremor, slowness of movement (bradykinesia), rigidity, and postural instability.

The most common presenting sign is a coarse slow tremor of the hand at rest which disappears during voluntary movement of the affected arm and in the deeper stages of sleep. It typically appears in only one hand, eventually affecting both hands as the disease progresses. Frequency of PD tremor is between 4 and 6 hertz (cycles per second). A feature of tremor is "pill-rolling", the tendency of the index finger and thumb to touch and perform together a circular movement. The term derives from the similarity between the movement of people with PD and the early pharmaceutical technique of manually making pills.

Bradykinesia (slowness of movement) is found in every case of PD, and is due to disturbances in motor planning of movement initiation, and associated with difficulties along the whole course of the movement process, from planning to initiation to execution of a movement. Performance of sequential and simultaneous movement is impaired. Bradykinesia is the most handicapping symptom of Parkinson’s disease leading to difficulties with everyday tasks such as dressing, feeding, and bathing. It leads to particular difficulty in carrying out two independent motor activities at the same time and can be made worse by emotional stress or concurrent illnesses. Paradoxically patients with Parkinson's disease can often ride a bicycle or climb stairs more easily than walk on a level. While most physicians may readily notice bradykinesia, formal assessment requires a patient to do repetitive movements with their fingers and feet.

Rigidity is stiffness and resistance to limb movement caused by increased muscle tone, an excessive and continuous contraction of muscles. In parkinsonism the rigidity can be uniform ("lead-pipe rigidity") or ratchety ("cogwheel rigidity"). The combination of tremor and increased tone is considered to be at the origin of cogwheel rigidity. Rigidity may be associated with joint pain; such pain being a frequent initial manifestation of the disease. In early stages of Parkinson's disease, rigidity is often asymmetrical and it tends to affect the neck and shoulder muscles prior to the muscles of the face and extremities. With the progression of the disease, rigidity typically affects the whole body and reduces the ability to move.

Postural instability is typical in the later stages of the disease, leading to impaired balance and frequent falls, and secondarily to bone fractures, loss of confidence, and reduced mobility. Instability is often absent in the initial stages, especially in younger people, especially prior to the development of bilateral symptoms. Up to 40% of people diagnosed with PD may experience falls and around 10% may have falls weekly, with the number of falls being related to the severity of PD.

Other recognized motor signs and symptoms include gait and posture disturbances such as festination (rapid shuffling steps and a forward-flexed posture when walking with no flexed arm swing). Freezing of gait (brief arrests when the feet seem to get stuck to the floor, especially on turning or changing direction), a slurred monotonous quiet voice, mask-like facial expression, and handwriting that gets smaller and smaller are other common signs.

Parkinson-plus syndromes, also known as disorders of multiple system degeneration, is a group of neurodegenerative diseases featuring the classical features of Parkinson's disease (tremor, rigidity, akinesia/bradykinesia, and postural instability) with additional features that distinguish them from simple idiopathic Parkinson's disease (PD). Some consider Alzheimer's disease to be in this group. Parkinson-plus syndromes are either inherited genetically or occur sporadically.

The atypical parkinsonian or Parkinson-plus syndromes are often difficult to differentiate from PD and each other. They include multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD). Dementia with Lewy bodies (DLB), may or may not be part of the PD spectrum, but it is increasingly recognized as the second-most common type of neurodegenerative dementia after Alzheimer's disease. These disorders are currently lumped into two groups, the synucleinopathies and the tauopathies. They may coexist with other pathologies.

Additional Parkinson-plus syndromes include Pick's disease and olivopontocerebellar atrophy. The latter is characterized by ataxia and dysarthria, and may occur either as an inherited disorder or as a variant of multiple system atrophy. MSA is also characterized by autonomic failure, formerly known as Shy–Drager syndrome.

Clinical features that distinguish Parkinson-plus syndromes from idiopathic PD include symmetrical onset, a lack of or irregular resting tremor, and a reduced response to dopaminergic drugs (including levodopa). Additional features include bradykinesia, early-onset postural instability, increased rigidity in axial muscles, dysautonomia, alien limb syndrome, supranuclear gaze palsy, apraxia, involvement of the cerebellum including the pyramidal cells, and in some instances significant cognitive impairment.

Some of the most prevalent symptom types in people exhibiting CBD pertain to identifiable movement disorders and problems with cortical processing. These symptoms are initial indicators of the presence of the disease. Each of the associated movement complications typically appear asymmetrically and the symptoms are not observed uniformly throughout the body. For example, a person exhibiting an alien hand syndrome (explained later) in one hand, will not correspondingly display the same symptom in the contralateral limb. Predominant movement disorders and cortical dysfunctions associated with CBD include:

- Parkinsonism

- Alien hand syndrome

- Apraxia (ideomotor apraxia and limb-kinetic apraxia)

- Aphasia

The presence of parkinsonism as a clinical symptom of CBD is largely responsible for complications in developing unique diagnostic criteria for the disease. Other such diseases in which parkinsonism forms an integral diagnostic characteristic are PD and PSP. Parkinsonism in CBD is largely present in an extremity such as the arm, and is always asymmetric. It has been suggested that non-dominant arm is involved more often. Common associated movement dysfunctions that comprise parkinsonism are rigidity, bradykinesia, and gait disorder, with limb rigidity forming the most typical manifestation of parkinsonism in CBD. Despite being relatively indistinct, this rigidity can lead to disturbances in gait and correlated movements. Bradykinesia in CBD occurs when there is notable slowing in the completion of certain movements in the limbs. In an associated study, it was determined that, three years following first diagnosis, 71% of persons with CBD demonstrate the presence of bradykinesia.

Differentiating some kinds of atypical Parkinson: Northwest Parkinson Foundation

Before Parkinson's disease is diagnosed, the differential diagnoses include:

- AIDS can sometimes lead to the symptoms of secondary parkinsonism, due to commonly causing dopaminergic dysfunction. Indeed, parkinsonism can be a presenting feature of HIV infection.

- Corticobasal degeneration

- Creutzfeldt–Jakob disease

- Dementia pugilistica or "boxer's dementia" is a condition that occurs in athletes due to chronic brain trauma.

- Diffuse Lewy body disease

- Drug-induced parkinsonism ("pseudoparkinsonism") due to drugs such as antipsychotics, metoclopramide, sertraline, fluoxetine or the toxin MPTP

- Encephalitis lethargica

- Essential tremor, an illness which has some diagnostic overlap with Parkinson's disease

- Orthostatic tremor

- MDMA addiction and frequent use has been linked to Parkonsonism. Several cases have been reported where individuals are diagnosed with the syndrome after taking MDMA.

- Multiple system atrophy

- Pantothenate kinase-associated neurodegeneration, also known as neurodegeneration with brain iron accumulation or Hallervorden-Spatz syndrome

- Parkinson plus syndrome

- Progressive supranuclear palsy

- Toxicity due to substances such as carbon monoxide, carbon disulfide, manganese, paraquat, mercury, hexane, rotenone, Annonaceae, and toluene (inhalant abuse: "huffing")

- Vascular parkinsonism, associated with underlying cerebrovascular disease

- Wilson's disease is a genetic disorder in which an abnormal accumulation of copper occurs. The excess copper can lead to the formation of a copper-dopamine complex, which leads to the oxidation of dopamine to aminochrome. The most common manifestations include bradykinesia, cogwheel rigidity and a lack of balance.

- Paraneoplastic syndrome: neurological symptoms caused by antibodies associated with cancers

- Genetic

- Rapid onset dystonia parkinsonism

- Parkin mutation

- X-linked dystonia parkinsonism

- Autosomal recessive juvenile parkinsonism

The presenting symptom of dementia with Lewy bodies is often cognitive dysfunction, though dementia eventually occurs in all individuals with DLB. In contrast to Alzheimer's disease (AD), in which memory loss is the first symptom, those with DLB first experience impaired attention, executive function, and visuospatial function, while memory is affected later. These impairments present as driving difficulty, such as becoming lost, misjudging distances, or as impaired job performance. In terms of cognitive testing, individuals may have problems with figure copying as a result of visuospatial impairment, with clock-drawing due to executive function impairment, and difficulty with serial sevens as a result of impaired attention. Short-term memory and orientation to time and place remain intact in the earlier stages of the disease.

While the specific symptoms in a person with DLB may vary, core features include: fluctuating cognition with great variations in attention and alertness from day to day and hour to hour, recurrent visual hallucinations (observed in 75% of people with DLB), and motor features of Parkinson's disease. Suggestive symptoms are rapid eye movement (REM)-sleep behavior disorder and abnormalities detected in PET or SPECT scans. REM sleep behavior disorder (RBD) often is a symptom first recognized by the patient's caretaker. RBD includes vivid dreaming, with persistent dreams, purposeful or violent movements, and falling out of bed. Benzodiazepines, anticholinergics, surgical anesthetics, some antidepressants, and over-the-counter drug cold remedies may cause acute confusion, delusions, and hallucinations.

Tremors are less common in DLB than in Parkinson's disease. Parkinsonian features may include shuffling gait, reduced arm-swing during walking, blank expression (reduced range of facial expression), stiffness of movements, ratchet-like cogwheeling movements, low speech volume, sialorrhea, and difficulty swallowing. Also, DLB patients often experience problems with orthostatic hypotension, including repeated falls, fainting, and transient loss of consciousness. Sleep-disordered breathing, a problem in multiple system atrophy, also may be a problem.

One of the most critical and distinctive clinical features of the disease is hypersensitivity to neuroleptic and antiemetic medications that affect dopaminergic and cholinergic systems. In the worst cases, a patient treated with these medications could become catatonic, lose cognitive function, or develop life-threatening muscle rigidity. Some commonly used medications that should be used with great caution, if at all, for people with DLB, are chlorpromazine, haloperidol, or thioridazine.

Visual hallucinations in people with DLB most commonly involve perception of people or animals that are not there, and may reflect Lewy bodies or AD pathology in the temporal lobe. Delusions may include reduplicative paramnesia and other elaborate misperceptions or misinterpretations. These hallucinations are not necessarily disturbing, and in some cases, the person with DLB may have insight into the hallucinations and even be amused by them, or be conscious they are not real. People with DLB also may have problems with vision, including double vision, and misinterpretation of what they see, for example, mistaking a pile of socks for snakes or a clothes closet for the bathroom.

Parkinsonism is a clinical syndrome characterized by tremor, bradykinesia, rigidity, and postural instability. Parkinsonism is found in Parkinson's disease (after which it is named), however a wide range of other causes may lead to this set of symptoms, including some toxins, a few metabolic diseases, and a handful of neurological conditions other than Parkinson's disease.

About 7% of people with parkinsonism have developed their symptoms following treatment with particular medications. Side effect of medications, mainly neuroleptic antipsychotics especially the phenothiazines (such as perphenazine and chlorpromazine), thioxanthenes (such as flupenthixol and zuclopenthixol) and butyrophenones (such as haloperidol), piperazines (such as ziprasidone), and rarely, antidepressants. The incidence of drug-induced parkinsonism increases with age. Drug-induced parkinsonism tends to remain at its presenting level, not progress like Parkinson's disease.

Accurate diagnosis of these Parkinson-plus syndromes is improved when precise diagnostic criteria are used. Since diagnosis of individual Parkinson-plus syndromes is difficult, the prognosis is often poor. Proper diagnosis of these neurodegenerative disorders is important as individual treatments vary depending on the condition. The nuclear medicine SPECT procedure using I-IBZM, is an effective tool in the establishment of the differential diagnosis between patients with PD and Parkinson-plus syndromes.

Dementia with Lewy bodies (DLB) is a type of dementia that worsens over time. Additional symptoms may include fluctuations in alertness, visual hallucinations, slowness of movement, trouble walking, and rigidity. Excessive movement during sleep and mood changes such as depression are also common.

The cause is unknown. Typically, no family history of the disease exists among those affected. The underlying mechanism involves the buildup of Lewy bodies, clumps of alpha-synuclein protein in neurons. It is classified as a neurodegenerative disorder. A diagnosis may be suspected based on symptoms, with blood tests and medical imaging done to rule out other possible causes. The differential diagnosis includes Parkinson's and Alzheimer's.

At present there is no cure. Treatments are supportive and attempt to relieve some of the motor and psychological symptoms associated with the disease. Acetylcholinesterase inhibitors, such as donepezil, may provide some benefit. Some motor problems may improve with levodopa. Antipsychotics, even for hallucinations, should generally be avoided due to side effects.

DLB is the most common cause of dementia after Alzheimer's disease and vascular dementia. It typically begins after the age of 50. About 0.1% of those over 65 are affected. Men appear to be more commonly affected than women. In the late part of the disease, people may depend entirely on others for their care. Life expectancy following diagnosis is about eight years. The abnormal deposits that cause the disease were discovered in 1912 by Frederic Lewy.

The initial symptoms in two-thirds of cases are loss of balance, lunging forward when mobilizing, fast walking, bumping into objects or people, and falls.

Other common early symptoms are changes in personality, general slowing of movement, and visual symptoms.

Later symptoms and signs are dementia (typically including loss of inhibition and ability to organize information), slurring of speech, difficulty swallowing, and difficulty moving the eyes, particularly in the vertical direction. The latter accounts for some of the falls experienced by these patients as they are unable to look up or down.

Some of the other signs are poor eyelid function, contracture of the facial muscles, a backward tilt of the head with stiffening of the , sleep disruption, urinary incontinence and constipation.

The visual symptoms are of particular importance in the diagnosis of this disorder. Patients typically complain of difficulty reading due to the inability to look down well. Notably, the ophthalmoparesis experienced by these patients mainly concerns voluntary eye movement and the inability to make vertical saccades, which is often worse with downward saccades. Patients tend to have difficulty looking down (a downgaze ) followed by the addition of an upgaze palsy. This vertical gaze paresis will correct when the examiner passively rolls the patient's head up and down as part of a test for the oculocephalic reflex. Involuntary eye movement, as elicited by Bell's phenomenon, for instance, may be closer to normal. On close inspection, eye movements called "square-wave jerks" may be visible when the patient fixes at distance. These are fine movements, that can be mistaken for nystagmus, except that they are saccadic in nature, with no smooth phase. Difficulties with convergence (convergence insufficiency), where the eyes come closer together while focusing on something near, like the pages of a book, is typical. Because the eyes have trouble coming together to focus at short distances, the patient may complain of diplopia (double vision) when reading.

Cardinal manifestations:

- Supranuclear ophthalmoplegia

- Neck dystonia

- Parkinsonism

- Pseudobulbar palsy

- Behavioral and cognitive impairment

- Imbalance and walking difficulty

- Frequent falls

PSP is frequently misdiagnosed as Parkinson's disease because of the slowed movements and gait difficulty, or as Alzheimer's disease because of the behavioral changes. It is one of a number of diseases collectively referred to as Parkinson plus syndromes. A poor response to levodopa along with symmetrical onset can help differentiate this disease from PD. Also, patients with the Richardson variant tend to have an upright or arched-back posture as opposed to the stooped-forward posture of other Parkinsonian disorders, although PSP-Parkinsonism (see below) may show the stooped posture. Early falls are characteristic, especially with Richardson-syndrome.

Tauopathy belongs to a class of neurodegenerative diseases associated with the pathological aggregation of tau protein in neurofibrillary or gliofibrillary tangles in the human brain. Tangles are formed by hyperphosphorylation of a microtubule-associated protein known as tau, causing it to aggregate in an insoluble form. (These aggregations of hyperphosphorylated tau protein are also referred to as paired helical filaments). The precise mechanism of tangle formation is not completely understood, and it is still controversial as to whether tangles are a primary causative factor in the disease or play a more peripheral role. Primary tauopathies, i.e., conditions in which neurofibrillary tangles (NFT) are predominantly observed, include:

- Primary age-related tauopathy (PART)/Neurofibrillary tangle-predominant senile dementia, with NFTs similar to AD, but without plaques.

- Chronic traumatic encephalopathy, including dementia pugilistica

- Progressive supranuclear palsy

- Corticobasal degeneration

- Frontotemporal dementia and parkinsonism linked to chromosome 17

- Lytico-Bodig disease (Parkinson-dementia complex of Guam)

- Ganglioglioma and gangliocytoma

- Meningioangiomatosis

- Postencephalitic parkinsonism

- Subacute sclerosing panencephalitis

- As well as lead encephalopathy, tuberous sclerosis, Hallervorden-Spatz disease, and lipofuscinosis

Neurofibrillary tangles were first described by Alois Alzheimer in one of his patients suffering from Alzheimer's disease (AD), which is considered a secondary tauopathy. AD is also classified as an amyloidosis because of the presence of senile plaques.

The degree of NFT involvement in AD is defined by Braak stages. Braak stages I and II are used when NFT involvement is confined mainly to the transentorhinal region of the brain, stages III and IV when there's also involvement of limbic regions such as the hippocampus, and V and VI when there's extensive neocortical involvement. This should not be confused with the degree of senile plaque involvement, which progresses differently.

In both Pick's disease and corticobasal degeneration, tau proteins are deposited as inclusion bodies within swollen or "ballooned" neurons.

Argyrophilic grain disease (AGD), another type of dementia, is marked by an abundance of argyrophilic grains and coiled bodies upon microscopic examination of brain tissue. Some consider it to be a type of Alzheimer's disease. It may co-exist with other tauopathies such as progressive supranuclear palsy and corticobasal degeneration, and also Pick's disease.

Huntington's disease (HD): a neurodegenerative disease caused by a CAG tripled expansion in the Huntington gene is the most recently described tauopathy (Fernandez-Nogales et al. Nat Med 2014). JJ Lucas and co-workers demonstrate that, in brains with HD, tau levels are increased and the 4R/3R balance is altered. In addition, the Lucas study shows intranuclear insoluble deposits of tau; these "Lucas' rods" were also found in brains with Alzheimer's disease.

Tauopathies are often overlapped with synucleinopathies, possibly due to interaction between the synuclein and tau proteins.

The non-Alzheimer's tauopathies are sometimes grouped together as "Pick's complex" due to their association with frontotemporal dementia, or frontotemporal lobar degeneration.

The prognosis and rate of the diseases progression vary considerably among individual patients and genetic kindreds, ranging from life expectancies of several months to several years, and, in exceptional cases, as long as two decades.

Kufor–Rakeb syndrome is an autosomal recessive disorder of juvenile onset also known as Parkinson disease-9 (PARK9).

Symptoms include supranuclear gaze palsy, spasticity, and dementia.

It can be associated with "ATP13A2". It is named after Kufr Rakeb in Irbid, Jordan.

Choreoathetosis is the occurrence of involuntary movements in a combination of chorea (irregular migrating contractions) and athetosis (twisting and writhing).

It is caused by many different diseases and agents. It is a symptom of several diseases, including Lesch-Nyhan Syndrome, phenylketonuria, and Huntington disease.

Choreoathetosis is also a common presentation of dyskinesia as a side effect of levodopa-carbidopa in the treatment of Parkinson disease.

Definitive diagnosis of FTDP-17 requires a combination of characteristic clinical and pathological features and molecular genetic analysis. Genetic counseling should be offered to affected and at-risk individuals; for most subtypes, penetrance is incomplete.

An individual displaying MERRFs syndrome will manifest not only a single symptom, but regularly patients display more than one affected body part at a time. It has been observed that patients with MERRF syndrome will primarily display Myoclonus as a first symptom, along with it they can also manifest seizures, cerebellar ataxia and myopathy. Secondary features include dementia, optic atrophy, bilateral deafness, peripheral neuropathy, spasticity or multiple lipomata. Additional symptoms include dementia, optic atrophy, bilateral deafness and peripheral neuropathy, spasticity, lipomatosis, and/or cardiomyopathy with wolff parkinson-white syndrome. Most patients will not exhibit all of these symptoms, however more than one of these symptoms will be present in a patient who has been diagnosed with MERRFS disease. Due to the multi-symptoms presented by the individual, the severity of the syndrome is very difficult to evaluate. Mitochondrial disorders may present at any age, and this holds truth for MERRS, since it forms part of them. Therefore, if a patient is presenting some of these symptoms, the doctor is able to narrow it down to MEERF mitochondrial disorder.

MERRF syndrome (or myoclonic epilepsy with ragged red fibers) is a mitochondrial disease. It is extremely rare, with an estimated prevalence of 1/4,000 in Northern Europe, and has varying degrees of expressivity owing to heteroplasmy. MERRF syndrome affects different parts of the body, particularly the muscles and nervous system. The signs and symptoms of this disorder appear at an early age, generally childhood or adolescence. The causes of MERRF syndrome is difficult to determine, however since its a mitochondrial disorder it can be caused by the mutation of nuclear DNA or mitochondrial DNA. The classification of this disease varies from patient to patient, since many individuals do not fall into one specific disease category.The primary features displayed on a person with MERRF include myoclonus, seizures, cerebellar ataxia, myopathy and ragged ref fibers (RRF) on muscle biopsy, leading to the diseases name. Secondary features include dementia, optic atrophy, bilateral deafness, peripheral neuropathy, spasticity or multiple lipomata. Mitochondrial disorders may present at any age, and this holds truth for MERRFS, since it forms part of them.

Onset : Early childhood

Progression: Chronic progressive

Clinical: Cerebellar ataxia plus syndrome / Optic Atrophy Plus Syndrome

Ocular: Optic atrophy, nystagmus, scotoma, and bilateral retrobulbar neuritis.

Other: Mental retardation, myoclonic epilepsy, spasticity, and posterior column sensory loss. Tremor in some cases.

Musculoskeletal

Contractures, lower limbs, Achilles tendon contractures, Hamstring contractures, Adductor longus contractures

Systemic

Hypogonadotrophic hypogonadism.

Infantile neuroaxonal dystrophy is a rare pervasive developmental disorder that primarily affects the nervous system. Individuals with infantile neuroaxonal dystrophy typically do not have any symptoms at birth, but between the ages of about 6 and 18 months they begin to experience delays in acquiring new motor and intellectual skills, such as crawling or beginning to speak. Eventually they lose previously acquired skills.

Behr syndrome is characterized by the association of early-onset optic atrophy with spinocerebellar degeneration resulting in ataxia, pyramidal signs, peripheral neuropathy and developmental delay.

Although it is an autosomal recessive disorder, heterozygotes may still manifest much attenuated symptoms. Autosomal dominant inheritance also being reported in a family. Recently a variant of OPA1 mutation with phenotypic presentation like Behr syndrome is also described. Some reported cases have been found to carry mutations in the OPA1, OPA3 or C12ORF65 genes which are known causes of pure optic atrophy or optic atrophy complicated by movement disorder.

Idiopathic generalized epilepsy (IGE) is a group of epileptic disorders that are believed to have a strong underlying genetic basis. Patients with an IGE subtype are typically otherwise normal and have no structural brain abnormalities. People also often have a family history of epilepsy and seem to have a genetically predisposed risk of seizures. IGE tends to manifest itself between early childhood and adolescence although it can be eventually diagnosed later. The genetic cause of some IGE types is known, though inheritance does not always follow a simple monogenic mechanism.

Symptom onset is usually rapid, often occurring within minutes of elevated serotonin levels. Serotonin syndrome encompasses a wide range of clinical findings. Mild symptoms may consist of increased heart rate, shivering, sweating, dilated pupils, myoclonus (intermittent jerking or twitching), as well as overresponsive reflexes. However, many of these symptoms may be side effects of the drug or drug interaction causing excessive levels of serotonin; not an effect of elevated serotonin itself. Tremor is a common side effect of MDMA's action on dopamine, whereas hyperreflexia is symptomatic of exposure to serotonin agonists. Moderate intoxication includes additional abnormalities such as hyperactive bowel sounds, high blood pressure and hyperthermia; a temperature as high as . The overactive reflexes and clonus in moderate cases may be greater in the lower limbs than in the upper limbs. Mental changes include hypervigilance or insomnia and agitation. Severe symptoms include severe increases in heart rate and blood pressure that may lead to shock. Temperature may rise to above in life-threatening cases. Other abnormalities include metabolic acidosis, rhabdomyolysis, seizures, renal failure, and disseminated intravascular coagulation; these effects usually arising as a consequence of hyperthermia.

The symptoms are often described as a clinical triad of abnormalities:

- Cognitive effects: headache, agitation, hypomania, mental confusion, hallucinations, coma

- Autonomic effects: shivering, sweating, hyperthermia, vasoconstriction, tachycardia, nausea, diarrhea.

- Somatic effects: myoclonus (muscle twitching), hyperreflexia (manifested by clonus), tremor.

This form of epilepsy is very rare, representing less than 1% of cases, and is twice as prevalent in boys compared to girls. Age of seizure onset is between 5 months and 5 years of age. Children with this disorder often present with head drops and brief arm jerks. Although there is believed to be a genetic basis for this disorder, no genetic linkage has been shown.