Epiconus Syndrome

Anatomically, the epiconus comprises the cord segment between L4 and S1, corresponding to the T12 and L1 vertebrae. The conus medullaris consists of the cord segment between S2 and S5 as well as coccygeal segments. The lumbosacral nerve roots are collectively termed the cauda equina wihch runs laterally and distally to the epiconus as well as the conus medullaris.

A lesion of the epiconus (L4 to S1 spinal cord segments) can produce, as weakness develops, a flaccid type paralysis with signs of lower motor neuron involvement. When the lesion involves the spinal cord above the epiconus, spastic paraesis as a sign of upper motor neuron dysfunction may also occur. Similarly, when the lesion involves the cord distal to the epiconus, bladder dysfunction, as a sign of conus medullaris compromise, and the cauda equina syndrome is usually evident on clinical presentation.

The epiconus syndrome presents with the following clinical features.

(1) A sensory disturbance in the leg (transverse, saddle, radicular, or socks type).

(2) Motor deficit as a sign of lower motor neuron involvement (foot drop, fasciculation, muscle atrophy).

(3) Diminished deep tendon reflexes.

(4) Occasional coexistence of positive pathological reflexes (Babinski's and Chaddock's signs).

(5) Diminished vibration sensation, and

(6) Bladder and bowel dysfunction.

In the presence of a dysfunctional conus medullaris, sensory disturbance in the perineal area (usually saddle type) and diminished vesicourethral as well as anorectal reflexes are significant findings. On the other hand, no significant abnormalities of voluntary leg movement and in deep tendon reflex activity are observed.

The cauda equina syndrome is a well recognised clinical entity with a flaccid type of paresis and/or intermittent neurogenic symptoms, and infrequently, parasympathetic disorders with unusual symptoms of penile erection as well as urinary incontinence.

The differential diagnosis should include old poliomyelitis, tethered cord syndrome as well as spinal dysraphism, amyotrophic lateral sclerosis, hereditary spastic paraplegia, hereditary sensorimotor neuropathy (Charcot-Marie-Tooth; Dejerine-Sottas), and spinal progressive muscular atrophy (Kennedy-Alter-Sung).

Rabbit Syndrome

Rabbit syndrome 
An antipsychotic-induced rhythmic motion of the mouth/lips, resembling the chewing movements of a rabbit. The movement consists of a vertical-only motion, at about 5Hz, with no involvement of the tongue. Usually, the involuntary movements associated with rabbit syndrome appear after a long period (in most cases months or years) of antipsychotic treatment; however, a few patients with the syndrome have had treatment histories with no antipsychotic involvement. 

The reported prevalence of rabbit syndrome ranges from 2.3 to 4.4% of patients treated with typical antipsychotics. There have been isolated reports of rabbit syndrome in patients treated with the atypical agents risperidone and clozapine. 

The most striking aspect of this syndrome is its specificity. Rabbit syndrome affects only the buccal region, and within this area it involves a highly stereotyped involuntary movement. This immediately focuses attention on the basal ganglia, in particular the substantia nigra pars reticulata, which is also implicated in oral dyskinesia. Continuing neurophysiological and pharmacological research of the basal ganglia holds the key to better understanding and treatment of this syndrome in the coming years.

Patients with rabbit syndrome are most often misdiagnosed as having oral tardive dyskinesia. In such cases the key for correct diagnosis is the involvement of tardive tongue movements, which does not occur in rabbit syndrome. 

The treatment of rabbit syndrome is empirical, reflecting poor understanding of its neuropathology. The first step is to reduce the amount of antipsychotic treatment as much as possible. However, since, in most cases, full withdrawal of antipsychotic treatment is impossible, the syndrome cannot be completely abolished without additional measures. The next stage of treatment involves specific drugs that aim to control the syndrome. Anticholinergic drugs are the best known treatment. Rabbit syndrome does not respond to treatment with levodopa or dopamine agonists. 

Stiff Person Syndrome

Stiff Person Syndrome

Occurs due to hyperexcitability of Anterior Horn Cells. Caused by interference of GABA mediated spinal cord inhibitory mechanisms. Symptoms are progressive, painful rigidity punctuated by intense muscle spasm. Affect the axial and paraspinal muscles. Symptoms limited to one limb.

The most common pathologic correlate is anti–glutamic acid decarboxylase (GAD) antibodies (It has been associated with a wide range of neurologic diseases). 
Additional possible pathophysiologic etiologies in patients negative for GAD antibody include postsynaptic elements such as synaptophysin, amphiphysin, gephyrin, and GABA-transaminase. 
It is also associated with a number of non-neurologic diseases, including diabetes mellitus and thyroiditis.

Additional Names- Synonyms

Stiff Person Syndrome- Stiff Man Syndrome,  Moersch Woltman syndrome

Double Crush Syndrome

Double Crush Syndrome

Once a nerve is damaged, it becomes more susceptible to injury elsewhere. The concept remains controversial e.g.
a. a pinched nerve in the neck from a herniated C6 disc increases likelihood of Carpal Tunnel syndrome in hand.
b. a patient with diabeticneuropathy have increased incidence of nerve entrapments in extremities.

If there are 2 points of nerve compression, then decompression of both the regions may be needed to optimize recovery.

While the exact pathophysiology is not known, it is possibly due to disturbance in axonal flow kinetics and the disruption of neurofilament architecture.

Milkmaid Grip

Milkmaid Grip

Milk maids grip is appreciated as an alternating squeezing and releasing of the finger like a milking motion, when asked to maintain a constant, firm grip of examiner's fingers, probably caused by combination of chorea and motor impersistence.

Inability to apply steady pressure during handshake leading to a characteristic squeeze and release of grip has been termed the milkmaid's grip. 

Similarly, patients have difficulty maintaining forced eyelid closure or sustained tongue protrusion. 

Huntington's disease is a progressive neurodegenerative trinucleotide repeat (CAG) disorder characterized by chorea, psychiatric disturbances, oculomotor dysfunction and cognitive decline. 

Motor exam often shows difficulty with fine motor skills and motor impersistence - the inability to maintain sustained voluntary contraction of a muscle group at a constant level. Motor impersistence occurs independently of chorea and has been shown to be linearly progressive over the course of disease suggesting a potential role as a surrogate marker of disease progression.

Also a finding typical of Sydenham’schorea, one of the Jones’ major criteria for diagnosing rheumatic fever

Introduction

This blog is meant for neurology tips and answers to questions asked during my DNB Neurology training.

Its personal, and not meant for teaching purposes. Accuracy and updates to existing information is not necessary.