Neurological Consultation and Movement Disorder Note

RE: Lachlan Thomas Vance

Dear Dr Eleanor Sterling

Thank you for referring this patient for assessment. Accompanied by his mother, Sarah Vance, and his father, David Vance Referred by Dr Eleanor Sterling

Although you are familiar with the patient's history, I will restate it for my records.

Lachlan presents today for evaluation of progressive diurnal gait abnormality, lower limb stiffness, and frequent falls over the past six months, alongside long-standing motor and vocal tics.

Lachlan was last entirely well regarding his ambulation approximately six months ago, prior to which he was an active child participating fully in school athletics. The onset of his gait disturbance was insidious, initially noticed by his parents as a tendency to drag his left foot late in the afternoon. Over the past three months, the symptoms have progressed to involve both lower limbs, characterised by inward turning of the feet and significant stiffness. The symptom pattern is markedly diurnal; Lachlan wakes up in the morning with near-normal mobility, walking independently without obvious posturing, but his symptoms steadily worsen from midday onwards, reaching peak severity by the early evening. Aggravating factors include prolonged physical exertion, running, and emotional stress, whereas rest and a full night of sleep provide substantial relief by the following morning. He has not experienced any weakness in his upper limbs, sensory loss, numbness, tingling, headaches, or seizures. Prior to this referral, he was assessed by a community physiotherapist who provided stretching exercises, which yielded minimal improvement in his afternoon symptoms.

Regarding his daytime motor fluctuations, during the first hour of the morning between 07:00 and 08:00, Lachlan exhibits normal posture and a fluid gait. He has not yet been trialled on dopaminergic medication, so response to a morning dose, degree of pharmacological improvement, duration of medication benefit, and medication-induced dyskinesia or adverse effects are not applicable at this stage. However, he develops a mild postural tremor in his outstretched hands by late afternoon. He does not experience true freezing of gait or a shuffling gait, but rather a dystonic, stiff-legged, equinovarus gait pattern that severely impairs his balance as the day progresses. This afternoon postural instability results in falls approximately three to four times per week, particularly when attempting to navigate stairs or uneven surfaces after school. His symptom severity is minimal in the morning, moderate by 13:00, and severe by 18:00, often requiring parental assistance to walk to the bathroom before bed. Once lying in bed before sleep, the cramping and abnormal posturing gradually subside, and he does not suffer from nocturnal leg spasms or disrupted sleep due to movement once asleep.

In terms of non-motor symptoms, Lachlan experiences mild initial insomnia related to evening anxiety and the urge to perform motor tics, though he maintains sleep well once settled. There are no memory or cognitive concerns; he is performing above average academically in Year Four. He has no urinary urgency, frequency, or incontinence. He experiences mild chronic constipation, passing hard stools every three days, without faecal incontinence. There is no history of visual or auditory hallucinations, delusions, psychosis, or impulse-control disorders. He complains of aching pain and cramping in both calves and arches of his feet during the late afternoon secondary to the sustained muscle contractions, without any clinical signs or symptoms of peripheral neuropathy.

Medical History

Lachlan was born at term via uncomplicated vaginal delivery following a normal pregnancy, and he achieved all early developmental motor and language milestones on time. He was diagnosed with Tourette syndrome at age eight years, manifesting as frequent eye blinking, shoulder shrugging, and throat clearing. He underwent an adenotonsillectomy at age five years at the Women's and Children's Hospital in Adelaide for obstructive sleep apnoea, with complete resolution of airway symptoms and an uneventful postoperative recovery. He has had no prior brain or spinal operations and no other hospital admissions.

Lachlan has a documented allergy to cefalexin, which causes a widespread urticarial rash. He has no known allergies to medications that affect the central or peripheral nervous system.

Lachlan lives in a single-storey suburban house in Adelaide with his parents and his twelve-year-old sister. He attends primary school full-time, where he is well-supported socially, though he has recently withdrawn from lunchtime soccer due to his afternoon mobility difficulties. As he is a nine-year-old child, there is no history of smoking, alcohol consumption, or recreational drug use. His family history is notable for a maternal uncle with childhood-onset motor tics and a paternal grandmother with mild essential tremor, but there is no known family history of early-onset Parkinson disease, dystonia, or metabolic neurological disorders.

Lachlan's quality of life has been moderately impacted by his inability to participate in afternoon sports and social activities with his peers, leading to frustration and mild social withdrawal. His parents hope that this consultation will provide a definitive unifying diagnosis and a targeted medical treatment plan that can restore his afternoon mobility and prevent further falls.

Medications

Lachlan currently takes clonidine (Catapres®) 50 micrograms orally once daily at 19:30 for management of his Tourette syndrome and associated sleep-onset difficulties, as well as macrogol 3350 (Movicol Junior®) one sachet orally once daily at 08:00 for constipation, and an over-the-counter cholecalciferol (Vitamin D3) 1,000 international units capsule orally once daily with breakfast.

Clinical Examination

At the time of this afternoon consultation at 15:30, Lachlan's vital signs were entirely stable, with a heart rate of 84 beats per minute, blood pressure of 102/64 mmHg sitting and 100/62 mmHg standing, respiratory rate of 18 breaths per minute, temperature of 36.7 °C, weight of 31.5 kg, and height of 136 cm.

On general examination, Lachlan was an alert, cooperative, and articulate nine-year-old boy who appeared well-nourished and had no dysmorphic features, neurocutaneous stigmata, or hepatosplenomegaly. Focused neurological assessment of mental status revealed full orientation to time, place, and person, with age-appropriate attention, intact memory, and fluent speech. He performed the Luria three-step motor sequence smoothly without perseveration after a single demonstration, and there was no evidence of visual, tactile, or auditory agnosia, nor any ideomotor or constructional apraxia. Cranial nerve examination from the second to the twelfth nerves was entirely unremarkable; visual fields were full to confrontation, fundoscopy showed crisp optic discs without Kayser-Fleischer rings on penlight inspection, facial sensation and expression were symmetrical, hearing was intact, and palate and tongue movements were midline and strong. Oculomotor function was completely normal, with full range of extraocular movements, no nystagmus, normal smooth pursuit, and rapid, accurate saccades without oculogyric crises. Motor function examination of the upper limbs revealed normal muscle bulk, normal tone without cogwheeling, and full 5/5 strength across all myotomes, though a fine postural tremor of the outstretched hands and intermittent bilateral shoulder-shrugging tics were observed. In the lower limbs, muscle bulk was normal, but there was marked, velocity-independent hypertonia and rigidity bilaterally, more pronounced on the left, accompanied by spontaneous dystonic inversion and plantarflexion of the left foot and extension of the great toe (striatal toe), despite preserved 5/5 power when he was able to overcome the dystonic posturing. Sensory examination to light touch, pinprick, vibration at the medial malleoli, and joint position sense at the great toes was completely intact and symmetrical. Deep tendon reflexes were symmetric and brisk (2+) at the biceps, triceps, brachioradialis, patellar, and Achilles tendons bilaterally, with flexor plantar responses when accounting for the spontaneous striatal toe posture. Coordination testing demonstrated intact finger-to-nose testing without dysmetria or intention tremor, rapid alternating movements in the hands were mildly slowed on the left due to subtle bradykinesia, and heel-to-shin testing was impaired bilaterally secondary to lower limb dystonic stiffness rather than true cerebellar ataxia. Gait assessment at 15:45 revealed a marked equinovarus dystonic gait with internal rotation of the left leg, reduced left arm swing, and a tendency to walk on the lateral border of the left foot and the toes of the right foot, which visibly worsened after walking twenty metres down the corridor.

Investigations

Prior investigations arranged by your practice and the local hospital include full blood count, electrolytes, renal function, liver function tests, thyroid function tests, and serum creatine kinase performed on 02/03/2026, all of which were within normal paediatric reference ranges. Serum ceruloplasmin and serum copper levels obtained on 02/03/2026 were normal at 0.28 g/L and 14.2 micromol/L respectively, effectively screening out Wilson disease. A magnetic resonance imaging scan of the brain and whole spine performed on 10/03/2026 under sedation demonstrated normal cerebral hemisphere, basal ganglia, brainstem, and cerebellar morphology, normal age-appropriate myelination, no pathological iron accumulation in the globus pallidus or substantia nigra, and an unremarkable spinal cord without tethering or syrinx. An electroencephalogram and electromyography have not been performed as there is no clinical suspicion of epilepsy or neuromuscular junction and peripheral nerve pathology.

Diagnostic Impression

1. Childhood-onset diurnal lower limb dystonia (suspected DOPA-responsive dystonia / Segawa disease) The primary assessment is clinically probable DOPA-responsive dystonia, most commonly caused by an autosomal dominant guanosine triphosphate cyclohydrolase 1 (GCH1) deficiency, given the classic presentation of childhood-onset lower limb dystonia beginning in the foot, prominent diurnal fluctuation with marked worsening in the afternoon and resolution after sleep, brisk lower limb reflexes with a striatal toe mimicking spastic diplegia, mild asymmetric bradykinesia, and a completely normal brain and spine magnetic resonance imaging study.

The differential diagnosis includes juvenile-onset parkinsonism secondary to PRKN or PINK1 mutations, DYT-TOR1A early-onset generalised dystonia, mild cerebral palsy (though excluded by the progressive diurnal course and normal perinatal history), and rarer neurotransmitter synthesis disorders such as tyrosine hydroxylase deficiency or sepiapterin reductase deficiency.

Diagnostic Plan

To confirm the diagnosis molecularly, I have arranged for a comprehensive next-generation sequencing dystonia and neurotransmitter gene panel (specifically targeting GCH1, TH, SPR, TOR1A, and PRKN) via peripheral blood draw today, alongside a diagnostic therapeutic trial of levodopa; a lumbar puncture for cerebrospinal fluid neurotransmitter metabolites will be deferred unless genetic testing and the levodopa trial prove inconclusive.

Treatment and Management Plan

We will initiate a diagnostic and therapeutic trial of levodopa/carbidopa (Sinemet® 100 mg/25 mg) starting at a low dose of one-quarter tablet (levodopa 25 mg / carbidopa 6.25 mg) orally twice daily at 08:00 and 13:00 for one week, increasing to half a tablet (levodopa 50 mg / carbidopa 12.5 mg) orally twice daily thereafter; the anticipated outcome in true DOPA-responsive dystonia is a dramatic and sustained resolution of the afternoon gait abnormality and stiffness within days to weeks, while possible adverse effects discussed include transient nausea, orthostatic light-headedness, and mild chorea or dyskinesia, the latter of which would simply require a dose reduction.

Lifestyle measures recommended today include pacing physical activities throughout the school day until the medication takes full effect, ensuring adequate hydration and dietary fibre intake to manage constipation, and advising the school to allow Lachlan extra time to transition between classrooms in the afternoon to prevent falls.

I have placed a referral to the Paediatric Medical Genetics service at the Women's and Children's Hospital for formal genetic counselling once the panel results return, and a referral to a paediatric neurological physiotherapist for gait reassessment once he is established on levodopa therapy.

I have scheduled a follow-up appointment in my clinic in four weeks on 17/04/2026 to review his clinical response to the levodopa/carbidopa trial, monitor for any medication side effects, and adjust the dosage as required, with a subsequent appointment to review the genetic panel results in three months.

2. Tourette syndrome Lachlan has a well-established diagnosis of Tourette syndrome characterised by chronic, waxing and waning motor and vocal tics that have been present for over one year and are currently reasonably well controlled, though occasionally exacerbated by evening fatigue.

The differential diagnosis for his repetitive movements includes transient tic disorder of childhood, obsessive-compulsive disorder rituals, and myoclonus, though the presence of premonitory urges and suppressibility confirms Tourette syndrome.

No further diagnostic investigations are required for his tic disorder at this time.

We will continue his current regimen of clonidine (Catapres®) 50 micrograms orally once daily at 19:30, as it provides satisfactory control of his evening tics and aids sleep onset without causing daytime sedation or hypotension, while monitoring closely to ensure that the introduction of levodopa does not inadvertently exacerbate his tic frequency.

Behavioural and lifestyle strategies reinforced with the family include maintaining a consistent bedtime routine, practising relaxation techniques before sleep, and avoiding drawing unnecessary attention to the tics at home and school.

No new specialist referrals are needed for his tics at present, though a referral to a clinical psychologist for Comprehensive Behavioural Intervention for Tics (CBIT) will be considered if his tics worsen in the future.

His tic severity and tolerance of dual therapy with clonidine and levodopa/carbidopa will be reviewed at his upcoming neurological follow-up appointment in four weeks.

Additional Notes:

Extensive education was provided to Lachlan and his parents regarding the nature of DOPA-responsive dystonia as a biochemical deficiency in dopamine synthesis rather than a neurodegenerative condition, emphasizing its favourable long-term prognosis, the expectation of returning to normal daily activities and sports, and the critical importance of strict adherence to the daily levodopa regimen.

The family was instructed to administer the levodopa/carbidopa with a small carbohydrate snack to minimise gastrointestinal upset, to keep a daily symptom diary recording his morning and afternoon gait quality, and to seek urgent medical care or contact our neurology department immediately if he experiences sudden severe generalised muscle spasms, acute inability to swallow or breathe, or severe uncontrolled involuntary movements after starting the medication.

Mrs and Mr Vance expressed significant concern that Lachlan's symptoms might represent a progressive, untreatable neurodegenerative disorder or affect his cognitive development, and they were greatly reassured to learn that DOPA-responsive dystonia spares cognition completely and typically responds extraordinarily well to low-dose replacement therapy.